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* Copyright 1988-2007 University of Washington
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
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<!--chtml set title="IMAP Toolkit Frequently Asked Questions"-->
<!--chtml include "//imap/incs/top.inc"-->
<h2>Table of Contents</h2>
<ul>
<li>
<a href="#general">1. General/Software Feature Questions</a>
<ul>
<li><a href="#1.1">1.1 Can I set up a POP or IMAP server on
UNIX/Linux/OSF/etc.?</a></li>
<li><a href="#1.2">1.2 I am currently using qpopper as my POP3 server
on UNIX. Do I need to replace it with ipop3d in order to run
imapd?</a></li>
<li><a href="#1.3">1.3 Can I set up a POP or IMAP server on Windows
XP, 2000, NT, Me, 98, or 95?</a></li>
<li><a href="#1.4">1.4 Can I set up a POP or IMAP server on Windows
3.1 or DOS?</a></li>
<li><a href="#1.5">1.5 Can I set up a POP or IMAP server on
Macintosh?</a></li>
<li><a href="#1.6">1.6 Can I set up a POP or IMAP server on
VAX/VMS?</a></li>
<li><a href="#1.7">1.7 Can I set up a POP or IMAP server on
TOPS-20?</a></li>
<li><a href="#1.8">1.8 Are hierarchical mailboxes supported?</a></li>
<li><a href="#1.9">1.9 Are "dual-use" mailboxes supported?</a></li>
<li><a href="#1.10">1.10 Can I have a mailbox that has both messages
and sub-mailboxes?</a></li>
<li><a href="#1.11">1.11 What is the difference between "mailbox" and
"folder"?</a></li>
<li><a href="#1.12">1.12 What is the status of
internationalization?</a></li>
<li><a href="#1.13">1.13 Can I use SSL?</a></li>
<li><a href="#1.14">1.14 Can I use TLS and the STARTTLS
facility?</a></li>
<li><a href="#1.15">1.15 Can I use CRAM-MD5 authentication?</a></li>
<li><a href="#1.16">1.16 Can I use APOP authentication?</a></li>
<li><a href="#1.17">1.17 Can I use Kerberos V5?</a></li>
<li><a href="#1.18">1.18 Can I use PAM for plaintext
passwords?</a></li>
<li><a href="#1.19">1.19 Can I use Kerberos 5 for plaintext
passwords?</a></li>
<li><a href="#1.20">1.20 Can I use AFS for plaintext
passwords?</a></li>
<li><a href="#1.21">1.21 Can I use DCE for plaintext
passwords?</a></li>
<li><a href="#1.22">1.22 Can I use the CRAM-MD5 database for
plaintext passwords?</a></li>
<li><a href="#1.23">1.23 Can I disable plaintext passwords?</a></li>
<li><a href="#1.24">1.24 Can I disable plaintext passwords on
unencrypted sessions, but allow them on encrypted sessions?</a></li>
<li><a href="#1.25">1.25 Can I use virtual hosts?</a></li>
<li><a href="#1.26">1.26 Can I use RPOP authentication?</a></li>
<li><a href="#1.27">1.27 Can I use Kerberos V4?</a></li>
<li><a href="#1.28">1.28 Is there support for S/Key or OTP?</a></li>
<li><a href="#1.29">1.29 Is there support for NTLM or SPA?</a></li>
<li><a href="#1.30">1.30 Is there support for mh?</a></li>
<li><a href="#1.31">1.31 Is there support for qmail and the maildir
format?</a></li>
<li><a href="#1.32">1.32 Is there support for the Cyrus mailbox
format?</a></li>
<li><a href="#1.33">1.33 Is this software Y2K compliant?</a></li>
</ul>
</li>
<li>
<a href="#requirements">2. What Do I Need to Build This Software?</a>
<ul>
<li><a href="#2.1">2.1 What do I need to build this software with SSL
on UNIX?</a></li>
<li><a href="#2.2">2.2 What do I need to build this software with
Kerberos V on UNIX?</a></li>
<li><a href="#2.3">2.3 What do I need to use a C++ compiler with this
software to build my own application?</a></li>
<li><a href="#2.4">2.4 What do I need to build this software on
Windows?</a></li>
<li><a href="#2.5">2.5 What do I need to build this software on
DOS?</a></li>
<li><a href="#2.6">2.6 Can't I use Borland C to build this software
on the PC?</a></li>
<li><a href="#2.7">2.7 What do I need to build this software on the
Mac?</a></li>
<li><a href="#2.8">2.8 What do I need to build this software on
VMS?</a></li>
<li><a href="#2.9">2.9 What do I need to build this software on
TOPS-20?</a></li>
<li><a href="#2.10">2.10 What do I need to build this software on
Amiga or OS/2?</a></li>
<li><a href="#2.11">2.11 What do I need to build this software on
Windows CE?</a></li>
</ul>
</li>
<li>
<a href="#build">3. Build and Configuration Questions</a>
<ul>
<li><a href="#3.1">3.1 How do I configure the IMAP and POP servers on
UNIX?</a></li>
<li><a href="#3.2">3.2 I built and installed the servers according to
the BUILD instructions. It can't be that easy. Don't I need to write
a config file?</a></li>
<li><a href="#3.3">3.3 How do I make the IMAP and POP servers look
for INBOX at some place other than the mail spool directory?</a></li>
<li><a href="#3.4">3.4 How do I make the IMAP server look for
secondary folders at some place other than the user's home
directory?</a></li>
<li><a href="#3.5">3.5 How do I configure SSL?</a></li>
<li><a href="#3.6">3.6 How do I configure TLS and the STARTTLS
facility?</a></li>
<li><a href="#3.7">3.7 How do I build/install OpenSSL and
obtain/create certificates for use with SSL?</a></li>
<li><a href="#3.8">3.8 How do I configure CRAM-MD5
authentication?</a></li>
<li><a href="#3.9">3.9 How do I configure APOP
authentication?</a></li>
<li><a href="#3.10">3.10 How do I configure Kerberos V5?</a></li>
<li><a href="#3.11">3.11 How do I configure PAM for plaintext
passwords?</a></li>
<li><a href="#3.12">3.12 It looks like all I have to do to make the
server use Kerberos is to build with PAM on my Linux system, and set
it up in PAM for Kerberos passwords. Right?</a></li>
<li><a href="#3.13">3.13 How do I configure Kerberos 5 for plaintext
passwords?</a></li>
<li><a href="#3.14">3.14 How do I configure AFS for plaintext
passwords?</a></li>
<li><a href="#3.15">3.15 How do I configure DCE for plaintext
passwords?</a></li>
<li><a href="#3.16">3.16 How do I configure the CRAM-MD5 database for
plaintext passwords?</a></li>
<li><a href="#3.17">3.17 How do I disable plaintext
passwords?</a></li>
<li><a href="#3.18">3.18 How do I disable plaintext passwords on
unencrypted sessions, but allow them in SSL or TLS sessions?</a></li>
<li><a href="#3.19">3.19 How do I configure virtual hosts?</a></li>
<li>
<a href="#3.20">3.20 Why do I get compiler warning messages such
as:
<ul>
<li>passing arg 3 of `scandir' from incompatible pointer
type</li>
<li>Pointers are not assignment-compatible.</li>
<li>Argument #4 is not the correct type.</li>
</ul>during the build?</a>
</li>
<li>
<a href="#3.21">3.21 Why do I get compiler warning messages such
as
<ul>
<li>Operation between types "void(*)(int)" and "void*" is not
allowed.</li>
<li>Function argument assignment between types "void*" and
"void(*)(int)" is not allowed.</li>
<li>Pointers are not assignment-compatible.</li>
<li>Argument #5 is not the correct type.</li>
</ul>during the build?</a>
</li>
<li>
<a href="#3.22">3.22 Why do I get linker warning messages such
as:
<ul>
<li>mtest.c:515: the `gets' function is dangerous and should not
be used.</li>
</ul>during the build? Isn't this a security bug?</a>
</li>
<li>
<a href="#3.23">3.23 Why do I get linker warning messages such
as:</a>
<ul>
<li>auth_ssl.c:92: the `tmpnam' function is dangerous and should
not be used.</li>
</ul>during the build? Isn't this a security bug?
</li>
<li><a href="#3.24">3.24 OK, suppose I see a warning message about a
function being "dangerous and should not be used" for something other
than this gets() or tmpnam() call?</a></li>
</ul>
</li>
<li>
<a href="#operation">4. Operational Questions</a>
<ul>
<li><a href="#4.1">4.1 How can I enable anonymous IMAP
logins?</a></li>
<li><a href="#4.2">4.2 How do I set up an alert message that each
IMAP user will see?</a></li>
<li><a href="#4.3">4.3 How does the c-client library choose which of
its several mechanisms to use to establish an IMAP connection to the
server? I noticed that it can connect on port 143, port 993, via rsh,
and via ssh.</a></li>
<li><a href="#4.4">4.4 I am using a TLS-capable IMAP server, so I
don't need to use /ssl to get encryption. However, I want to be
certain that my session is TLS encrypted before I send my password.
How to I do this?</a></li>
<li><a href="#4.5">4.5 How do I use one of the alternative formats
described in the formats.txt document? In particular, I hear that mbx
format will give me better performance and allow shared
access.</a></li>
<li><a href="#4.6">4.6 How do I set up shared mailboxes?</a></li>
<li><a href="#4.7">4.7 How can I make the server syslogs go to
someplace other than the mail syslog?</a></li>
</ul>
</li>
<li>
<a href="#security">5. Security Questions</a>
<ul>
<li><a href="#5.1">5.1 I see that the IMAP server allows access to
arbitary files on the system, including /etc/passwd! How do I disable
this?</a></li>
<li><a href="#5.2">5.2 I've heard that IMAP servers are insecure. Is
this true?</a></li>
<li><a href="#5.3">5.3 How do I know that I have the most secure
version of the server?</a></li>
<li><a href="#5.4">5.4 I see all these strcpy() and sprintf() calls,
those are unsafe, aren't they?</a></li>
<li><a href="#5.5">5.5 Those /tmp lock files are protected 666, is
that really right?</a></li>
</ul>
</li>
<li>
<a href="#strange">6. <i>Why Did You Do This Strange Thing?</i>
Questions</a>
<ul>
<li><a href="#6.1">6.1 Why don't you use GNU autoconfig / automake /
autoblurdybloop?</a></li>
<li><a href="#6.2">6.2 Why do you insist upon a build with -g?
Doesn't it waste disk and memory space?</a></li>
<li><a href="#6.3">6.3 Why don't you make c-client a shared
library?</a></li>
<li><a href="#6.4">6.4 Why don't you use iconv() for
internationalization support?</a></li>
<li><a href="#6.5">6.5 Why is the IMAP server connected to the home
directory by default?</a></li>
<li><a href="#6.6">6.6 I have a Windows system. Why isn't the server
plug and play for me?</a></li>
<li><a href="#6.7">6.7 I looked at the UNIX SSL code and saw that you
have the SSL data payload size set to 8192 bytes. SSL allows 16K; why
aren't you using the full size?</a></li>
<li><a href="#6.8">6.8 Why is an mh format INBOX called #mhinbox
instead of just INBOX?</a></li>
<li><a href="#6.9">6.9 Why don't you support the maildir
format?</a></li>
<li><a href="#6.10">6.10 Why don't you support the Cyrus
format?</a></li>
<li><a href="#6.11">6.11 Why is it creating extra forks on my SVR4
system?</a></li>
<li><a href="#6.12">6.12 Why are you so fussy about the date/time
format in the internal <code>"From&nbsp;"</code> line in traditional
UNIX mailbox files? My other mail program just considers every line
that starts with <code>"From&nbsp;"</code> to be the start of the
message.</a></li>
<li><a href="#6.13">6.13 Why is traditional UNIX format the default
format?</a></li>
<li><a href="#6.14">6.14 Why do you write this "DON'T DELETE THIS
MESSAGE -- FOLDER INTERNAL DATA" message at the start of traditional
UNIX and MMDF format mailboxes?</a></li>
<li><a href="#6.15">6.15 Why don't you stash the mailbox metadata in
the first real message of the mailbox instead of writing this fake
FOLDER INTERNAL DATA message?</a></li>
<li><a href="#6.16">6.16 Why aren't "dual-use" mailboxes the
default?</a></li>
<li><a href="#6.17">6.17 Why do you use ucbcc to build on
Solaris?</a></li>
<li><a href="#6.18">6.18 Why should I care about some old system with
BSD libraries? cc is the right thing on my Solaris system!</a></li>
<li><a href="#6.19">6.19 Why do you insist upon writing .lock files
in the spool directory?</a></li>
<li><a href="#6.20">6.20 Why should I care about compatibility with
the past?</a></li>
</ul>
</li>
<li>
<a href="#problems">7. Problems and Annoyances</a>
<ul>
<li><a href="#7.1">7.1 Help! My INBOX is empty! What happened to my
messages?</a></li>
<li><a href="#7.2">7.2 Help! All my messages in a non-INBOX mailbox
have been concatenated into one message which claims to be from me
and has a subject of the file name of the mailbox! What's going
on?</a></li>
<li>
<a href="#7.3">7.3 Why do I get the message:
<ul>
<li>CREATE failed: Can't create mailbox node xxxxxxxxx: File
exists</li>
</ul>and how do I fix it?</a>
</li>
<li><a href="#7.4">7.4 Why can't I log in to the server? The user
name and password are right!</a></li>
<li><a href="#7.5">7.5 Help! My load average is soaring and I see
hundreds of POP and IMAP servers, many logged in as the same
user!</a></li>
<li><a href="#7.6">7.6 Why does mail disappear even though I set
"keep mail on server"?</a></li>
<li>
<a href="#7.7">7.7 Why do I get the message
<ul>
<li>Moved ##### bytes of new mail to /home/user/mbox from
/var/spool/mail/user</li>
</ul>and why did this happen?</a>
</li>
<li><a href="#7.8">7.8 Why isn't it showing the local host name as a
fully-qualified domain name?</a></li>
<li><a href="#7.9">7.9 Why is the local host name in the
From/Sender/Message-ID headers of outgoing mail not coming out as a
fully-qualified domain name?</a></li>
<li>
<a href="#7.10">7.10 What does the message:
<ul>
<li>Mailbox vulnerable - directory /var/spool/mail must have 1777
protection</li>
</ul>mean? How can I fix this?</a>
</li>
<li>
<a href="#7.11">7.11 What does the message:
<ul>
<li>Mailbox is open by another process, access is readonly</li>
</ul>mean? How do I fix this?</a>
</li>
<li>
<a href="#7.12">7.12 What does the message:
<ul>
<li>Can't get write access to mailbox, access is readonly</li>
</ul>mean?</a>
</li>
<li><a href="#7.13">7.13 I set my POP3 client to "delete messages
from server" but they never get deleted. What is wrong?</a></li>
<li>
<a href="#7.14">7.14 What do messages such as:
<ul>
<li>Message ... UID ... already has UID ...</li>
<li>Message ... UID ... less than ...</li>
<li>Message ... UID ... greater than last ...</li>
<li>Invalid UID ... in message ..., rebuilding UIDs</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.15">7.15 What do the error messages:
<ul>
<li>Unable to read internal header at ...</li>
<li>Unable to find CRLF at ...</li>
<li>Unable to parse internal header at ...</li>
<li>Unable to parse message date at ...</li>
<li>Unable to parse message flags at ...</li>
<li>Unable to parse message UID at ...</li>
<li>Unable to parse message size at ...</li>
<li>Last message (at ... ) runs past end of file ...</li>
</ul>mean? I am using mbx format.</a>
</li>
<li>
<a href="#7.16">7.16 What do the syslog messages:
<ul>
<li>imap/tcp server failing (looping)</li>
<li>pop3/tcp server failing (looping)</li>
</ul>mean? When it happens, the listed service shuts down. How can
I fix this?</a>
</li>
<li>
<a href="#7.17">7.17 What does the syslog message:
<ul>
<li>Mailbox lock file /tmp/.600.1df3 open failure: Permission
denied</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.18">7.18 What do the syslog messages:
<ul>
<li>Command stream end of file, while reading line user=...
host=...</li>
<li>Command stream end of file, while reading char user=...
host=...</li>
<li>Command stream end of file, while writing text user=...
host=...</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.19">7.19 Why did my POP or IMAP session suddenly
disconnect? The syslog has the message:
<ul>
<li>Killed (lost mailbox lock) user=... host=...</li>
</ul></a>
</li>
<li><a href="#7.20">7.20 Why does my IMAP client show all the files
on the system, recursively from the UNIX root directory?</a></li>
<li><a href="#7.21">7.21 Why does my IMAP client show all of my
files, recursively from my UNIX home directory?</a></li>
<li><a href="#7.22">7.22 Why does my IMAP client show that I have
mailboxes named "#mhinbox", "#mh", "#shared", "#ftp", "#news", and
"#public"?</a></li>
<li><a href="#7.23">7.23 Why does my IMAP client show all my files in
my home directory?</a></li>
<li><a href="#7.24">7.24 Why is there a long delay before I get
connected to the IMAP or POP server, no matter what client I
use?</a></li>
<li><a href="#7.25">7.25 Why is there a long delay in Pine or any
other c-client based application call before I get connected to the
IMAP server? The hang seems to be in the c-client mail_open() call. I
don't have this problem with any other IMAP client. There is no delay
connecting to a POP3 or NNTP server with mail_open().</a></li>
<li><a href="#7.26">7.26 Why does a message sometimes get split into
two or more messages on my SUN system?</a></li>
<li>
<a href="#7.27">7.27 Why did my POP or IMAP session suddenly
disconnect? The syslog has the message:
<ul>
<li>Autologout user=&lt;...my user name...&gt; host=&lt;...my
imap server...&gt;</li>
</ul></a>
</li>
<li>
<a href="#7.28">7.28 What does the UNIX error message:
<ul>
<li>TLS/SSL failure: myserver: SSL negotiation failed</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.29">7.29 What does the PC error message:
<ul>
<li>TLS/SSL failure: myserver: Unexpected TCP input
disconnect</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.30">7.30 What does the error message:
<ul>
<li>TLS/SSL failure: myserver: Server name does not match
certificate</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.31">7.31 What does the UNIX error message:
<ul>
<li>TLS/SSL failure: myserver: self-signed certificate</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.32">7.32 What does the PC error message
<ul>
<li>TLS/SSL failure: myserver: Self-signed certificate or
untrusted authority</li>
</ul>mean?</a>
</li>
<li>
<a href="#7.33">7.33 What does the UNIX error message:
<ul>
<li>TLS/SSL failure: myserver: unable to get local issuer
certificate</li>
</ul>mean?</a>
</li>
<li><a href="#7.34">7.34 Why does reading certain messages hang when
using Netscape? It works fine with Pine!</a></li>
<li><a href="#7.35">7.35 Why does Netscape say that there's a problem
with the IMAP server and that I should "Contact your mail server
administrator."?</a></li>
<li><a href="#7.36">7.36 Why is one user creating huge numbers of
IMAP or POP server sessions?</a></li>
<li><a href="#7.37">7.37 Why don't I get any new mail notifications
from Outlook Express or Outlook after a while?</a></li>
<li><a href="#7.38">7.38 Why don't I get any new mail notifications
from Entourage?</a></li>
<li><a href="#7.39">7.39 Why doesn't Entourage work at all?</a></li>
<li><a href="#7.40">7.40 Why doesn't Netscape Notify (NSNOTIFY.EXE)
work at all?</a></li>
<li><a href="#7.41">7.41 Why can't I connect via SSL to Eudora? It
says the connection has been broken, and in the server syslogs I see
"Command stream end of file".</a></li>
<li><a href="#7.42">7.42 Sheesh. Aren't there <i>any</i> good IMAP
clients out there?</a></li>
<li>
<a href="#7.43">7.43 But wait! PC Pine (or other PC program build
with c-client) crashes with the message
<ul>
<li>incomplete SecBuffer exceeds maximum buffer size</li>
</ul>when I use SSL connections. This is a bug in c-client, right?</a>
</li>
<li><a href="#7.44">7.44 My qpopper users keep on getting the DON'T
DELETE THIS MESSAGE -- FOLDER INTERNAL DATA if they also use Pine or
IMAP. How can I fix this?</a></li>
<li><a href="#7.45">7.45 Help! I installed the servers but I can't
connect to them from my client!</a></li>
<li>
<a href="#7.46">7.46 Why do I get the message
<ul>
<li>Can not authenticate to SMTP server: 421 SMTP connection went
away!</li>
</ul>and why did this happen? There was also something about
<ul>
<li>SECURITY PROBLEM: insecure server advertised AUTH=PLAIN</li>
</ul></a>
</li>
<li>
<a href="#7.47">7.47 Why do I get the message
<ul>
<li>SMTP Authentication cancelled</li>
</ul>and why did this happen? There was also something about
<ul>
<li>SECURITY PROBLEM: insecure server advertised AUTH=PLAIN</li>
</ul></a>
</li>
<li>
<a href="#7.48">7.48 Why do I get the message
<ul>
<li>Invalid base64 string</li>
</ul>when I try to authenticate to a Cyrus server?
</li></a>
</ul>
</li>
<li>
<a href="#additional">8. Where to Go For Additional Information</a>
<ul>
<li><a href="#8.1">8.1 Where can I go to ask questions?</a></li>
<li><a href="#8.2">8.2 I have some ideas for enhancements to IMAP.
Where should I go?</a></li>
<li><a href="#8.3">8.3 Where can I read more about IMAP and other
email protocols?</a></li>
<li><a href="#8.4">8.4 Where can I find out more about setting up and
administering an IMAP server?</a></li>
</ul>
</li>
</ul><!--=======START BODY-->
<hr>
<h2><a name="general">1. General/Software Feature Questions</a></h2>
<hr>
<p><a name="1.1"><strong>1.1 Can I set up a POP or IMAP server on
UNIX/Linux/OSF/etc.?</strong></a></p>
<dl>
<dd>Yes. Refer to the UNIX specific notes in files CONFIG and BUILD.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.2"><strong>1.2 I am currently using qpopper as my POP3 server on
UNIX. Do I need to replace it with ipop3d in order to run
imapd?</strong></a></p>
<dl>
<dd>
Not necessarily.
<p>Although ipop3d interoperates with imapd better than qpopper, imapd
and qpopper will work together. The few qpopper/imapd interoperability
issues mostly affect users who use both IMAP and POP3 clients; those
users would probably be better served if their POP3 server is
ipop3d.</p>
<p>If you are happy with qpopper and just want to add imapd, you should
do that, and defer a decision on changing qpopper to ipop3d. That way,
you can get comfortable with imapd's performance, without changing
anything for your qpopper users.</p>
<p>Many sites have subsequently decided to change from qpopper to
ipop3d in order to get better POP3/IMAP interoperability. If you need
to do this, you'll know. There also seems to be a way to make qpopper
work better with imapd; see the answer to the <a href="#7.44">My
qpopper users keep on getting the DON'T DELETE THIS MESSAGE -- FOLDER
INTERNAL DATA if they also use Pine or IMAP. How can I fix this?</a>
question.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.3"><strong>1.3 Can I set up a POP or IMAP server on Windows XP,
2000, NT, Me, 98, or 95?</strong></a></p>
<dl>
<dd>
Yes. Refer to the NT specific notes in files CONFIG and BUILD. Also,
for DOS-based versions of Windows (Windows Me, 98, and 95) you *must*
set up CRAM-MD5 authentication, as described in md5.txt.
<p>There is no file access control on Windows 9x or Me, so you probably
will have to do modifications to env_unix.c to prevent people from
hacking others' mail.</p>
<p>Note, however, that the server is not plug and play the way it is
for UNIX.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.4"><strong>1.4 Can I set up a POP or IMAP server on Windows 3.1 or
DOS?</strong></a><br>
<a name="1.5"><strong>1.5 Can I set up a POP or IMAP server on
Macintosh?</strong></a><br>
<a name="1.6"><strong>1.6 Can I set up a POP or IMAP server on
VAX/VMS?</strong></a></p>
<dl>
<dd>Yes, it's just a small matter of programming.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.7"><strong>1.7 Can I set up a POP or IMAP server on
TOPS-20?</strong></a></p>
<dl>
<dd>
You have a TOPS-20 system? Cool.
<p>If IMAP2 (RFC 1176) is good enough for you, you can use MAPSER which
is about the ultimate gonzo pure TOPS-20 extended addressing assembly
language program. Unfortunately, IMAP2 is barely good enough for Pine
these days, and most other IMAP clients won't work with IMAP2 at all.
Maybe someone will hack MAPSER to do IMAP4rev1 some day.</p>
<p>We don't know if anyone wrote a POP3 server for TOPS-20. There
definitely was a POP2 server once upon a time.</p>
<p>Or you can port the POP and IMAP server from this IMAP toolkit to
it. All that you need for a first stab is to port the MTX driver.
That'll probably be just a couple of hours of hacking.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.8"><strong>1.8 Are hierarchical mailboxes
supported?</strong></a><br>
<a name="1.9"><strong>1.9 Are "dual-use" mailboxes
supported?</strong></a><br>
<a name="1.10"><strong>1.10 Can I have a mailbox that has both messages and
sub-mailboxes?</strong></a></p>
<dl>
<dd>
Yes. However, there is one important caveat.
<p>Some mailbox formats, including the default which is the traditional
UNIX mailbox format, are stored as a single file containing all the
messages. UNIX does not permit a name in the filesystem to be both a
file and a directory; consequently you can not have a sub-mailbox
within a mailbox that is in one of these formats.</p>
<p>This is not a limitation of the software; this is a limitation of
UNIX. For example, there are mailbox formats in which the name is a
directory and each message is a file within that directory; these
formats support sub-mailboxes within such mailboxes. However, for
technical reasons, the "flat file" formats are generally preferred
since they perform better. Read imap-2007/docs/formats.txt for more
information on this topic.</p>
<p>It is always permissible to create a directory that is not a
mailbox, and have sub-mailboxes under it. The easiest way to create a
directory is to create a new mailbox inside a directory that doesn't
already exist. For example, if you create "Mail/testbox" on UNIX, the
directory "Mail/" will automatically be created and then the mailbox
"testbox" will be created as a sub-mailbox of "Mail/".</p>
<p>It is also possible to create the name "Mail/" directly. Check the
documentation for your client software to see how to do this with that
software.</p>
<p>Of course, on Windows systems you would use "\" instead of "/".</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.11"><strong>1.11 What is the difference between "mailbox" and
"folder"?</strong></a></p>
<dl>
<dd>
The term "mailbox" is IMAP-speak for what a lot of software calls a
"folder" or a "mail folder". However, "folder" is often used in other
contexts to refer to a directory, for example, in the graphic user
interface on both Windows and Macintosh.
<p>A "mailbox" is specifically defined as a named object that contains
messages. It is not required to be capable of containing other types of
objects including other mailboxes; although some mailbox formats will
permit this.</p>
<p>In IMAP-speak, a mailbox which can not contain other mailboxes is
called a "no-inferiors mailbox". Similarly, a directory which can not
contain messages is not a mailbox and is called a "no-select name".</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.12"><strong>1.12 What is the status of
internationalization?</strong></a></p>
<dl>
<dd>
The IMAP toolkit is partially internationalized and multilingualized.
<p>Searching is supported in the following charsets: US-ASCII, UTF-8,
ISO-8859-1, ISO-8859-2, ISO-8859-3, ISO-8859-4, ISO-8859-5, ISO-8859-6,
ISO-8859-7, ISO-8859-8, ISO-8859-9, ISO-8859-10, ISO-8859-11,
ISO-8859-13, ISO-8859-14, ISO-8859-15, ISO-8859-16, KOI8-R, KOI8-U
(alias KOI8-RU), TIS-620, VISCII, ISO-2022-JP, ISO-2022-KR,
ISO-2022-CN, ISO-2022-JP-1, ISO-2022-JP-2, GB2312 (alias CN-GB),
CN-GB-12345, BIG5 (alias CN-BIG5), EUC-JP, EUC-KR, Shift_JIS,
Shift-JIS, KS_C_5601-1987, KS_C_5601-1992, WINDOWS_874, WINDOWS-1250,
WINDOWS-1251, WINDOWS-1252, WINDOWS-1253, WINDOWS-1254, WINDOWS-1255,
WINDOWS-1256, WINDOWS-1257, WINDOWS-1258.</p>
<p>All ISO-2022-?? charsets are treated identically, and support ASCII,
JIS Roman, hankaku katakana, ISO-8859-[1 - 10], TIS, GB 2312, JIS X
0208, JIS X 0212, KSC 5601, and planes 1 and 2 of CNS 11643.</p>
<p>EUC-JP includes support for JIS X 0212 and hankaku katakana.</p>
<p>c-client library support also exists to convert text in any of the
above charsets into Unicode, including headers with MIME
encoded-words.</p>
<p>There is no support for localization (e.g. non-English error
messages) at the present time, but such support is planned.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.13"><strong>1.13 Can I use SSL?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.5">How do I configure SSL?</a>
question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.14"><strong>1.14 Can I use TLS and the STARTTLS
facility?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.6">How do I configure TLS and
the STARTTLS facility?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.15"><strong>1.15 Can I use CRAM-MD5
authentication?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.8">How do I configure CRAM-MD5
authentication?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.16"><strong>1.16 Can I use APOP authentication?</strong></a></p>
<dl>
<dd>
Yes. See the <a href="#3.9">How do I configure APOP authentication?</a>
question.
<p>Note that there is no client support for APOP authentication.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.17"><strong>1.17 Can I use Kerberos V5?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.10">How do I configure
Kerberos V5?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.18"><strong>1.18 Can I use PAM for plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.11">How do I configure PAM for
plaintext passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.19"><strong>1.19 Can I use Kerberos 5 for plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.13">How do I configure
Kerberos 5 for plaintext passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.20"><strong>1.20 Can I use AFS for plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.14">How do I configure AFS for
plaintext passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.21"><strong>1.21 Can I use DCE for plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.15">How do I configure DCE for
plaintext passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.22"><strong>1.22 Can I use the CRAM-MD5 database for plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.16">How do I configure the
CRAM-MD5 database for plaintext passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.23"><strong>1.23 Can I disable plaintext
passwords?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.17">How do I disable plaintext
passwords?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.24"><strong>1.24 Can I disable plaintext passwords on unencrypted
sessions, but allow them on encrypted sessions?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.18">How do I disable plaintext
passwords on unencrypted sessions, but allow them in SSL or TLS
sessions?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.25"><strong>1.25 Can I use virtual hosts?</strong></a></p>
<dl>
<dd>Yes. See the answer to the <a href="#3.19">How do I configure virtual
hosts?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.26"><strong>1.26 Can I use RPOP authentication?</strong></a></p>
<dl>
<dd>There is no support for RPOP authentication.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.27"><strong>1.27 Can I use Kerberos V4?</strong></a></p>
<dl>
<dd>
Kerberos V4 is not supported. Kerberos V4 client-only contributed code
is available in
<pre>
<a href=
"ftp://ftp.cac.washington.edu/mail/kerberos4-patches.tar.Z">ftp://ftp.cac.washington.edu/mail/kerberos4-patches.tar.Z
</a>
</pre>This is a patchkit which must be applied to the IMAP toolkit according
to the instructions in the patchkit's README. We can not promise that this
code works.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.28"><strong>1.28 Is there support for S/Key or
OTP?</strong></a></p>
<dl>
<dd>There is currently no support for S/Key or OTP. There may be an OTP
SASL authenticator available from third parties.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.29"><strong>1.29 Is there support for NTLM or
SPA?</strong></a></p>
<dl>
<dd>
There is currently no support for NTLM or SPA, nor are there any plans
to add such support. In general, I avoid vendor-specific mechanisms. I
also believe that these mechanisms are being deprecated by their
vendor.
<p>There may be an NTLM SASL authenticator available from third
parties.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.30"><strong>1.30 Is there support for mh?</strong></a></p>
<dl>
<dd>
Yes, but only as a legacy format. Your mh format INBOX is accessed by
the name "#mhinbox", and all other mh format mailboxes are accessed by
prefixing "#mh/" to the name, e.g. "#mh/foo". The mh support uses the
"Path:" entry in your .mh_profile file to identify the root directory
of your mh format mailboxes.
<p>Non-legacy use of mh format is not encouraged. There is no support
for permanent flags or unique identifiers; furthermore there are known
severe performance problems with the mh format.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.31"><strong>1.31 Is there support for qmail and the maildir
format?</strong></a></p>
<dl>
<dd>There is no support for qmail or the maildir format in our
distribution, nor are there any plans to add such support. Maildir
support may be available from third parties.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.32"><strong>1.32 Is there support for the Cyrus mailbox
format?</strong></a></p>
<dl>
<dd>No.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="1.33"><strong>1.33 Is this software Y2K compliant?</strong></a></p>
<dl>
<dd>Please read the files Y2K and calendar.txt.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="requirements">2. What Do I Need to Build This Software?</a></h2>
<hr>
<p><a name="2.1"><strong>2.1 What do I need to build this software with SSL on
UNIX?</strong></a></p>
<dl>
<dd>You need to build and install OpenSSL first.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.2"><strong>2.2 What do I need to build this software with Kerberos
V on UNIX?</strong></a></p>
<dl>
<dd>You need to build and install MIT Kerberos first.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.3"><strong>2.3 What do I need to use a C++ compiler with this
software to build my own application?</strong></a></p>
<dl>
<dd>
If you are building an application using the c-client library, use the
new c-client.h file instead of including the other include files. It
seems that c-client.h should define away all the troublesome names that
conflict with C++.
<p>If you use gcc, you may need to use -fno-operator-names as well.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.4"><strong>2.4 What do I need to build this software on
Windows?</strong></a></p>
<dl>
<dd>
You need Microsoft Visual C++ 6.0, Visual C++ .NET, or Visual C# .NET
(which you can buy from any computer store), along with the Microsoft
Platform SDK (which you can download from Microsoft's web site).
<p>You do not need to install the entire Platform SDK; it suffices to
install just the Core SDK and the Internet Development SDK.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.5"><strong>2.5 What do I need to build this software on
DOS?</strong></a></p>
<dl>
<dd>It's been several years since we last attempted to do this. At the
time, we used Microsoft C.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.6"><strong>2.6 Can't I use Borland C to build this software on the
PC?</strong></a></p>
<dl>
<dd>Probably not. If you know otherwise, please let us know.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.7"><strong>2.7 What do I need to build this software on the
Mac?</strong></a></p>
<dl>
<dd>It has been several years since we last attempted to do this. At the
time, we used Symantec THINK C; but today you'll need a C compiler which
allows segments to be more than 32K.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.8"><strong>2.8 What do I need to build this software on
VMS?</strong></a></p>
<dl>
<dd>You need the VMS C compiler, and either the Multinet or Netlib
TCP.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.9"><strong>2.9 What do I need to build this software on
TOPS-20?</strong></a></p>
<dl>
<dd>You need the TOPS-20 KCC compiler.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.10"><strong>2.10 What do I need to build this software on Amiga or
OS/2?</strong></a></p>
<dl>
<dd>We don't know.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="2.11"><strong>2.11 What do I need to build this software on Windows
CE?</strong></a></p>
<dl>
<dd>This port is incomplete. Someone needs to finish it.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="build">3. Build and Configuration Questions</a></h2>
<hr>
<p><a name="3.1"><strong>3.1 How do I configure the IMAP and POP servers on
UNIX?</strong></a><br>
<a name="3.2"><strong>3.2 I built and installed the servers according to the
BUILD instructions. It can't be that easy. Don't I need to write a
config file?</strong></a></p>
<dl>
<dd>
For ordinary "vanilla" UNIX systems, this software is plug and play;
just build it, install it, and you're done. If you have a modified
system, then you may want to do additional work; most of this is to a
single source code file (env_unix.c on UNIX systems). Read the file
CONFIG for more details.
<p>Yes, it's that easy. There are some additional options, such as SSL
or Kerberos, which require additional steps to build. See the relevant
questions below.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.3"><strong>3.3 How do I make the IMAP and POP servers look for
INBOX at some place other than the mail spool
directory?</strong></a><br>
<a name="3.4"><strong>3.4 How do I make the IMAP server look for secondary
folders at some place other than the user's home
directory?</strong></a></p>
<dl>
<dd>Please read the file CONFIG for discussion of this and other
issues.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.5"><strong>3.5 How do I configure SSL?</strong></a><br>
<a name="3.6"><strong>3.6 How do I configure TLS and the STARTTLS
facility?</strong></a></p>
<dl>
<dd>
imap-2007 supports SSL and TLS client functionality on UNIX and 32-bit
Windows for IMAP, POP3, SMTP, and NNTP; and SSL and TLS server
functionality on UNIX for IMAP and POP3.
<p>UNIX SSL build requires that a third-party software package,
OpenSSL, be installed on the system first. Read imap-2007/docs/SSLBUILD
for more information.</p>
<p>SSL is supported via undocumented Microsoft interfaces in Windows 9x
and NT4; and via standard interfaces in Windows 2000, Windows
Millenium, and Windows XP.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.7"><strong>3.7 How do I build/install OpenSSL and obtain/create
certificates for use with SSL?</strong></a></p>
<dl>
<dd>If you need help in doing this, try the contacts mentioned in the
OpenSSL README. We do not offer support for OpenSSL or certificates.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.8"><strong>3.8 How do I configure CRAM-MD5
authentication?</strong></a><br>
<a name="3.9"><strong>3.9 How do I configure APOP
authentication?</strong></a></p>
<dl>
<dd>
CRAM-MD5 authentication is enabled in the IMAP and POP3 client code on
all platforms. Read md5.txt to learn how to set up CRAM-MD5 and APOP
authentication on UNIX and NT servers.
<p>There is no support for APOP client authentication.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.10"><strong>3.10 How do I configure Kerberos V5?</strong></a></p>
<dl>
<dd>
imap-2007 supports client and server functionality on UNIX and 32-bit
Windows.
<p>Kerberos V5 is supported by default in Windows 2000 builds:</p>
<pre>
nmake -f makefile.w2k
</pre>
<p>Other builds require that a third-party Kerberos package, e.g. MIT
Kerberos, be installed on the system first.</p>
<p>To build with Kerberos V5 on UNIX, include EXTRAAUTHENTICATORS=gss
in the make command line, e.g.</p>
<pre>
make lnp EXTRAAUTHENTICATORS=gss
</pre>
<p>To build with Kerberos V5 on Windows 9x, Windows Millenium, and NT4,
use the "makefile.ntk" file instead of "makefile.nt":</p>
<pre>
nmake -f makefile.ntk
</pre>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.11"><strong>3.11 How do I configure PAM for plaintext
passwords?</strong></a></p>
<dl>
<dd>
On Linux systems, use the lnp port, e.g.
<pre>
make lnp
</pre>On Solaris systems and other systems with defective PAM
implementations, build with PASSWDTYPE=pmb, e.g.
<pre>
make sol PASSWDTYPE=pmb
</pre>On all other systems, build with PASSWDTYPE=pam, e.g
<pre>
make foo PASSWDTYPE=pam
</pre>If you build with PASSWDTYPE=pam and authentication does not work, try
rebuilding (after a "make clean") with PASSWDTYPE=pmb.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.12"><strong>3.12 It looks like all I have to do to make the server
use Kerberos is to build with PAM on my Linux system, and set it up in
PAM for Kerberos passwords. Right?</strong></a></p>
<dl>
<dd>
Yes and no.
<p>Doing this will make plaintext password authentication use the
Kerberos password instead of the /etc/passwd password.</p>
<p>However, this will NOT give you Kerberos-secure authentication. See
the answer to the <a href="#3.10">How do I configure Kerberos V5?</a>
question for how to build with Kerberos-secure authentication.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.13"><strong>3.13 How do I configure Kerberos 5 for plaintext
passwords?</strong></a></p>
<dl>
<dd>
Build with PASSWDTYPE=gss, e.g.
<pre>
make sol PASSWDTYPE=gss
</pre>However, this will NOT give you Kerberos-secure authentication. See the
answer to the <a href="#3.10">How do I configure Kerberos V5?</a> question
for how to build with Kerberos-secure authentication.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.14"><strong>3.14 How do I configure AFS for plaintext
passwords?</strong></a></p>
<dl>
<dd>
Build with PASSWDTYPE=afs, e.g
<pre>
make sol PASSWDTYPE=afs
</pre>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.15"><strong>3.15 How do I configure DCE for plaintext
passwords?</strong></a></p>
<dl>
<dd>
Build with PASSWDTYPE=dce, e.g
<pre>
make sol PASSWDTYPE=dce
</pre>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.16"><strong>3.16 How do I configure the CRAM-MD5 database for
plaintext passwords?</strong></a></p>
<dl>
<dd>
The CRAM-MD5 password database is automatically used for plaintext
password if it exists.
<p>Note that this is NOT CRAM-MD5-secure authentication. You probably
want to consider disabling plaintext passwords for non-SSL/TLS
sessions. See the next two questions.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.17"><strong>3.17 How do I disable plaintext
passwords?</strong></a></p>
<dl>
<dd>
Server-level plaintext passwords can be disabled by setting
PASSWDTYPE=nul, e.g.
<pre>
make lnx EXTRAAUTHENTICATORS=gss PASSWDTYPE=nul
</pre>Note that you must have a CRAM-MD5 database installed or specify at
least one EXTRAAUTHENTICATOR, otherwise it will not be possible to log in to
the server.
<p>When plaintext passwords are disabled, the IMAP server will
advertise the LOGINDISABLED capability and the POP3 server will not
advertise the USER capability.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<p><a name="3.18"><strong>3.18 How do I disable plaintext passwords on
unencrypted sessions, but allow them in SSL or TLS
sessions?</strong></a></p>
<dl>
<dd>
<p>Do not set PASSWDTYPE=nul or SSLTYPE=unix. Set SSLTYPE=nopwd
instead, e.g.</p>
<pre>
make lnx SSLTYPE=nopwd
</pre>
<p>When plaintext passwords are disabled, the IMAP server will
advertise the LOGINDISABLED capability and the POP3 server will not
advertise the USER capability.</p>
<p>Plaintext passwords will always be enabled in SSL sessions; the IMAP
server will not advertise the LOGINDISABLED capability and the POP3
server will advertise the USER capability.</p>
<p>If the client does a successful start-TLS in a non-SSL session,
plaintext passwords will be enabled, and a new CAPABILITY or CAPA
command (which is required after start-TLS) will show the effect as in
SSL sessions.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.19"><strong>3.19 How do I configure virtual
hosts?</strong></a></p>
<dl>
<dd>
This is automatic, but with certain restrictions.
<p>The most important one is that each virtual host must have its own
IP address; otherwise the server has no way of knowing which virtual
host is desired.</p>
<p>As distributed, the software uses a global password file; hence user
"fred" on one virtual host is "fred" on all virtual hosts. You may want
to modify the checkpw() routine to implement some other policy (e.g.
separate password files).</p>
<p>Note that the security model assumes that all users have their own
unique UNIX UID number. So if you use separate password files you
should make certain that the UID numbers do not overlap between
different files.</p>
<p>More advanced virtual host support may be available as patches from
third parties.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.20"><strong>3.20 Why do I get compiler warning messages such
as:</strong></a></p>
<pre>
passing arg 3 of `scandir' from incompatible pointer type
Pointers are not assignment-compatible.
Argument #4 is not the correct type.
</pre>
<p><strong>during the build?</strong></p>
<dl>
<dd>
You can safely ignore these messages.
<p>Over the years, the prototype for scandir() has changed, and thus is
variant across different UNIX platforms. In particular, the definitions
of the third argument (type select_t) and fourth argument (type
compar_t) have changed over the years, the issue being whether or not
the arguments to the functions pointed to by these function pointers
are of type const or not.</p>
<p>The way that c-client calls scandir() will tend to generate these
compiler warnings on newer systems such as Linux; however, it will
still build. The problem with fixing the call is that then it won't
build on older systems.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.21"><strong>3.21 Why do I get compiler warning messages such
as</strong></a></p>
<pre>
Operation between types "void(*)(int)" and "void*" is not allowed.
Function argument assignment between types "void*" and "void(*)(int)" is not allowed.
Pointers are not assignment-compatible.
Argument #5 is not the correct type.
</pre>
<p><strong>during the build?</strong></p>
<dl>
<dd>
You can safely ignore these messages.
<p>All known systems have no problem with casting a function pointer
to/from a void* pointer, certain C compilers issue a compiler
diagnostic because this facility is listed as a "Common extension" by
the C standard:</p>
<pre>
K.5.7 Function pointer casts
[#1] A pointer to an object or to void may be cast to a pointer
to a function, allowing data to be invoked as a function (6.3.4).
[#2] A pointer to a function may be cast to a pointer to an
object or to void, allowing a function to be inspected or
modified (for example, by a debugger) (6.3.4).
</pre>It may be just a "common extension", but this facility is relied upon
heavily by c-client.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.22"><strong>3.22 Why do I get linker warning messages such
as:</strong></a></p>
<pre>
mtest.c:515: the `gets' function is dangerous and should not be used.
</pre>
<p><strong>during the build? Isn't this a security bug?</strong></p>
<dl>
<dd>
You can safely ignore this message.
<p>Certain linkers, most notably on Linux, give this warning message.
It is indeed true that the traditional gets() function is not a safe
one.</p>
<p>However, the mtest program is only a demonstration program, a model
of a very basic application program using c-client. It is not something
that you would install, much less run in any security-sensitive
context.</p>
<p>mtest has numerous other shortcuts that you wouldn't want to do in a
real application program.</p>
<p>The only "security bug" with mtest would be if it was run by some
script in a security-sensitive context, but mtest isn't particularly
useful for such purposes. If you wanted to write a script to automate
some email task using c-client, you'd be better off using imapd instead
of mtest.</p>
<p>mtest only has two legitimate uses. It's a useful testbed for me
when debugging new versions of c-client, and it's useful as a model for
someone writing a simple c-client application to see how the various
calls work.</p>
<p>By the way, if you need a more advanced example of c-client
programming than mtest (and you probably will), I recommend that you
look at the source code for imapd and Pine.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.23"><strong>3.23 Why do I get linker warning messages such
as:</strong></a></p>
<pre>
auth_ssl.c:92: the `tmpnam' function is dangerous and should not be used.
</pre>
<p><strong>during the build? Isn't this a security bug?</strong></p>
<dl>
<dd>
You can safely ignore this message.
<p>Certain linkers, most notably on Linux, give this warning message,
based upon two known issues with tmpnam():</p>
<dl>
<dd>there can be a buffer overflow if an inadequate buffer is
allocated.</dd>
<dd>there can be a timing race caused by certain incautious usage of
the return value.</dd>
</dl>
<p>Neither of these issues applies in the particular use that is made
of tmpnam(). More importantly, the tmpnam() call is never executed on
Linux systems.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="3.24"><strong>3.24 OK, suppose I see a warning message about a
function being "dangerous and should not be used" for something other
than this gets() or tmpnam() call?</strong></a></p>
<dl>
<dd>Please forward the details for investigation.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="operation">4. Operational Questions</a></h2>
<hr>
<p><a name="4.1"><strong>4.1 How can I enable anonymous IMAP
logins?</strong></a></p>
<dl>
<dd>Create the file /etc/anonymous.newsgroups. At the present time, this
file should be empty. This will permit IMAP logins as anonymous as well
as the ANONYMOUS SASL authenticator. Anonymous users have access to
mailboxes in the #news., #ftp/, and #public/ namespaces only.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.2"><strong>4.2 How do I set up an alert message that each IMAP
user will see?</strong></a></p>
<dl>
<dd>Create the file /etc/imapd.alert with the text of the message. This
text should be kept to one line if possible. Note that this will cause an
alert to every IMAP user every time they initiate an IMAP session, so it
should only be used for critical messages.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.3"><strong>4.3 How does the c-client library choose which of its
several mechanisms to use to establish an IMAP connection to the server?
I noticed that it can connect on port 143, port 993, via rsh, and via
ssh.</strong></a></p>
<dl>
<dd>
c-client chooses how to establish an IMAP connection via the following
rules:
<ul>
<li>If /ssl is specified, use an SSL connection. Fail otherwise.</li>
<li>Else if client is a UNIX system and "ssh server exec /etc/rimapd"
works, use that</li>
<li>Else if /tryssl is specified and an SSL connection works, use
that.</li>
<li>Else if client is a UNIX system and "rsh server exec /etc/rimapd"
works, use that.</li>
<li>Else use a non-SSL connection.</li>
</ul>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.4"><strong>4.4 I am using a TLS-capable IMAP server, so I don't
need to use /ssl to get encryption. However, I want to be certain that
my session is TLS encrypted before I send my password. How to I do
this?</strong></a></p>
<dl>
<dd>Use the /tls option in the mailbox name. This will cause an error
message and the connection to fail if the server does not negotiate
STARTTLS.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.5"><strong>4.5 How do I use one of the alternative formats
described in the formats.txt document? In particular, I hear that mbx
format will give me better performance and allow shared
access.</strong></a></p>
<dl>
<dd>
The rumors about mbx format being preferred are true. It is faster than
the traditional UNIX mailbox format and permits shared access.
<p>However, and this is <em>very important</em>, note that using an
alternative mailbox format is an advanced facility, and only expert
users should undertake it. If you don't understand any of the following
notes, you may not be enough of an expert yet, and are probably better
off not going this route until you are more comfortable with your
understanding.</p>
<p>Some of the formats, including mbx, are only supported by the
software based on the c-client library, and are not recognized by other
mailbox programs. The "vi" editor will corrupt any mbx format mailbox
that it encounters.</p>
<p>Another problem is that the certain formats, including mbx, use
advanced file access and locking techniques that do <em>not</em> work
reliably with NFS. NFS is not a real filesystem. Use IMAP instead of
NFS for distributed access.</p>
<p>Each of the following steps are in escalating order of involvement.
The further you go down this list, the more deeply committed you
become:</p>
<ul>
<li>The simplest way to create a mbx-format mailbox is to prefix the
name with "#driver.mbx/" when creating a mailbox through c-client.
For example, if you create "#driver.mbx/foo", the mailbox "foo" will
be created in mbx format. Only use "#driver.mbx/" when creating the
mailbox. At all other times, just use the name ("foo" in this
example); the software will automatically select the driver for mbx
whenever that mailbox is accessed without you doing anything
else.</li>
<li>You can use the "mailutil copy" command to copy an existing
mailbox to a new mailbox in mbx format. Read the man page provided
with the mailutil program for details.</li>
<li>If you create an mbx-format INBOX, by creating
"#driver.mbx/INBOX" (note that "INBOX" must be all uppercase), then
subsequent access to INBOX by any c-client based application will use
the mbx-format INBOX. Any mail delivered to the traditional format
mailbox in the spool directory (e.g. /var/spool/mail/$USER) will
automatically be copied into the mbx-format INBOX and the spool
directory copy removed.</li>
<li>You can cause any newly-created mailboxes to be in mbx-format by
default by changing the definition of CREATEPROTO=unixproto to be
CREATEPROTO=mbxproto in src/osdep/unix/Makefile, then rebuilding the
IMAP toolkit (do a "make clean" first). Do not change EMPTYPROTO,
since mbx format mailboxes are never a zero-byte file. If you use
Pine or the imap-utils, you should probably also rebuild them with
the new IMAP toolkit too.</li>
<li>You can deliver directly to the mbx-format INBOX by use of the
tmail or dmail programs. tmail is for direct invocation from sendmail
(or whatever MTA program you use); dmail is for calls from procmail.
Both of these programs have man pages which must be read carefully
before making this change.</li>
</ul>
<p>Most other servers (e.g. Cyrus) require use of a non-standard
format. A full-fledged format conversion is not significantly different
from what you have to do with other servers. The difference, which
makes format conversion procedures somewhat more complicated with this
server, is that there is no "all or nothing" requirement with this
server. There are many points in between. A format conversion can be
anything from a single mailbox or single user, to systemwide.</p>
<p>This is good in that you can decide how far to go, or do the steps
incrementally as you become more comfortable with the result. On the
other hand, there's no "One True Way" which can be boiled down to a
simple set of pedagogical instructions.</p>
<p>A number of sites have done full-fledged format conversions, and are
reportedly quite happy with the results. Feel free to ask in the
comp.mail.imap newsgroup or the imap-uw mailing list for advice or
help.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.6"><strong>4.6 How do I set up shared mailboxes?</strong></a></p>
<dl>
<dd>
At the simplest level, a shared mailbox is one which has UNIX file and
directory protections which permit multiple users to access it. What
this means is that your existing skills and tools to create and manage
shared files on your UNIX system apply to shared mailboxes; e.g.
<pre>
chmod 666 mailbox
</pre>
<p>You may want to consider the use of a mailbox format which permits
multiple simultaneous read/write sessions, such as the mbx format. The
traditional UNIX format only allows one read/write session to a
mailbox at a time.</p>
<p>An additional convenience item are three system directories, which
can be set up for shared namespaces. These are: #ftp, #shared, and
#public, and are defined by creating the associated UNIX users and home
directories as described below.</p>
<p>#ftp/ refers to the anonymous ftp filesystem exported by the ftp
server, and is equivalent to the home directory for UNIX user "ftp".
For example, #ftp/foo/bar refers to the file /foo/bar in the anonymous
FTP filesystem, or ~ftp/foo/bar for normal users. Anonymous FTP files
are available to anonymous IMAP logins. By default, newly-created files
in #ftp/ are protected 644.</p>
<p>#public/ refers to an IMAP toolkit convention called "public" files,
and is equivalent to the home directory for UNIX user "imappublic". For
example, #public/foo/bar refers to the file ~imappublic/foo/bar. Public
files are available to anonymous IMAP logins. By default, newly-created
files in #public are created with protection 0666.</p>
<p>#shared/ refers to an IMAP toolkit convention called "shared" files,
and is equivalent to the home directory for UNIX user "imapshared". For
example, #shared/foo/bar refers to the file ~imapshared/foo/bar. Shared
files are <em>not</em> available to anonymous IMAP logins. By default,
newly-created files in #shared are created with protection 0660.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="4.7"><strong>4.7 How can I make the server syslogs go to someplace
other than the mail syslog?</strong></a></p>
<dl>
<dd>
The openlog() call that sets the syslog facility is in
<strong>src/osdep/unix/env_unix.c</strong> in routine
<strong>server_init()</strong>. You need to edit this file to change
the syslog facility from LOG_MAIL to the facility you want, then
rebuild. You also need to set up your /etc/syslog.conf properly.
<p>Refer to the man pages for syslog and syslogd for more information
on what the available syslog facilities are and how to configure
syslogs. If you still don't understand what to do, find a UNIX system
expert.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="security">5. Security Questions</a></h2>
<hr>
<p><a name="5.1"><strong>5.1 I see that the IMAP server allows access to
arbitary files on the system, including /etc/passwd! How do I disable
this?</strong></a></p>
<dl>
<dd>
You should not worry about this if your IMAP users are allowed shell
access. The IMAP server does not permit any access that the user can
not have via the shell.
<p>If, and only if, you deny your IMAP users shell access, you may want
to consider one of three choices. Note that these choices reduce IMAP
functionality, and may have undesirable side effects. Each of these
choices involves an edit to file
<strong>src/osdep/unix/env_unix.c</strong></p>
<p>The first (and recommended) choice is to set
<strong>restrictBox</strong> as described in file CONFIG. This will
disable access to the filesystem root, to other users' home directory,
and to superior directory.</p>
<p>The second (and strongly NOT recommended) choice is to set
<strong>closedBox</strong> as described in file CONFIG. This puts each
IMAP session into a so-called "chroot jail", and thus setting this
option is <em>extremely</em> dangerous; it can make your system much
less secure and open to root compromise attacks. So do not use this
option unless you are <em>absolutely certain</em> that you understand
all the issues of a "chroot jail."</p>
<p>The third choice is to rewrite routine
<strong>mailboxfile()</strong> to implement whatever mapping from
mailbox name to filesystem name (and restrictions) that you wish. This
is the most general choice. As a guide, you can see at the start of
routine <strong>mailboxfile()</strong> what the
<strong>restrictBox</strong> choice does.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="5.2"><strong>5.2 I've heard that IMAP servers are insecure. Is this
true?</strong></a></p>
<dl>
<dd>
There are no known security problems in this version of the IMAP
toolkit, including the IMAP and POP servers. The IMAP and POP servers
limit what can be done while not logged in, and as part of the login
process discard all privileges except those of the user.
<p>As with other software packages, there have been buffer overflow
vulnerabilities in past versions. All known problems of this nature are
fixed in this version.</p>
<p>There is every reason to believe that the bad guys are engaged in an
ongoing effort to find vulnerabilities in the IMAP toolkit. We look for
such problems, and when one is found we fix it.</p>
<p>It's unfortunate that any vulnerabilities existed in past versions,
and we're doing my best to keep the IMAP toolkit free of
vulnerabilities. No new vulnerabilities have been discovered in quite a
while, but efforts will not be relaxed.</p>
<p>Beware of vendors who claim that their implementations can not have
vulnerabilities.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="5.3"><strong>5.3 How do I know that I have the most secure version
of the server?</strong></a></p>
<dl>
<dd>
The best way is to keep your server software up to date. The bad guys
are always looking for ways to crack software, and when they find one,
let all their friends know.
<p>Oldtimers used to refer to a concept of <em>software rot</em>: if
your software hasn't been updated in a while, it would "rot" -- tend to
acquire problems that it didn't have when it was new.</p>
<p>The latest release version of the IMAP toolkit is always available
at <a href=
"ftp://ftp.cac.washington.edu/mail/imap.tar.Z">ftp://ftp.cac.washington.edu/mail/imap.tar.Z</a></p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="5.4"><strong>5.4 I see all these strcpy() and sprintf() calls, those
are unsafe, aren't they?</strong></a></p>
<dl>
<dd>
Yes and no.
<p>It can be unsafe to do these calls if you do not know that the
string being written will fit in the buffer. However, they are
perfectly safe if you do know that.</p>
<p>Beware of programmers who advocate doing a brute-force change of all
instances of</p>
<pre>
strcpy (s,t);
</pre>to
<pre>
strncpy (s,t,n)[n] = '\0';
</pre>and similar measures in the name of "fixing all possible buffer
overflows."
<p>There are examples in which a security bug was introduced because of
this type of "fix", due to the programmer using the wrong value for n.
In one case, the programmer thought that n was larger than it actually
was, causing a NUL to be written out of the buffer; in another, n was
too small, and a security credential was truncated.</p>
<p>What is particularly ironic was that in both cases, the original
strcpy() was safe, because the size of the source string was known to
be safe.</p>
<p>With all this in mind, the software has been inspected, and it is
believed that all places where buffer overflows can happen have been
fixed. The strcpy()s that are still are in the code occur after a size
check was done in some other way.</p>
<p>Note that the common C idiom of</p>
<pre>
*s++ = c;
</pre>is just as vulnerable to buffer overflows. You can't cure buffer
overflows by outlawing certain functions, nor is it desirable to do so;
sometimes operations like strcpy() translate into fast machine instructions
for better performance.
<p>Nothing replaces careful study of code. That's how the bad guys find
bugs. Security is not accomplished by means of brute-force
shortcuts.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="5.5"><strong>5.5 Those /tmp lock files are protected 666, is that
really right?</strong></a></p>
<dl>
<dd>
Yes. Shared mailboxes won't work otherwise. Also, you get into
accidental denial of service problems with old lock files left lying
around; this happens fairly frequently.
<p>The deliberate mischief that can be caused by fiddling with the lock
files is small-scale; harassment level at most. There are many -- and
much more effective -- other ways of harassing another user on UNIX.
It's usually not difficult to determine the culprit.</p>
<p>Before worrying about deliberate mischief, worry first about things
happening by accident!</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="strange">6. <em>Why Did You Do This Strange Thing?</em>
Questions</a></h2>
<hr>
<p><a name="6.1"><strong>6.1 Why don't you use GNU autoconfig / automake /
autoblurdybloop?</strong></a></p>
<dl>
<dd>
Autoconfig et al are not available on all the platforms where the IMAP
toolkit is supported; and do not work correctly on some of the
platforms where they do exist. Furthermore, these programs add another
layer of complexity to an already complex process.
<p>Coaxing software that uses autoconfig to build properly on platforms
which were not specifically considered by that software wastes an
inordinate amount of time. When (not if) autoconfig fails to do the
right thing, the result is an inpenetrable morass to untangle in order
to find the problem and fix it.</p>
<p>The concept behind autoconfig is good, but the execution is flawed.
It rarely does the right thing on a platform that wasn't specifically
considered. Human life is too short to debug autoconfig problems,
especially since the current mechanism is so much easier.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.2"><strong>6.2 Why do you insist upon a build with -g? Doesn't it
waste disk and memory space?</strong></a></p>
<dl>
<dd>
From time to time a submitted port has snuck in without -g. This has
<em>always</em> ended up causing problems. There are only two valid
excuses for not using -g in a port:
<ul>
<li>The compiler does not support -g</li>
<li>An alternate form of -g is needed with optimization, e.g.
-g3.</li>
</ul>
<p>There will be no new ports added without -g (or a suitable
alternative) being set.</p>
<p>-g has not been arbitrarily added to the ports which do not
currently have it because we don't know if doing so would break the
build. However, any support issues with one of those port <em>will</em>
lead to the correct -g setting being determined and permanently
added.</p>
<p>Processors are fast enough (and disk space is cheap enough) that -g
should be automatic in all compilers with no way of turning it off, and
/bin/strip should be a symlink to /bin/true. Human life is too short to
deal with binaries built without -g. Such binaries should be a bad
memory of the days of KIPS processors and disks that costs several
dollars per kilobyte.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.3"><strong>6.3 Why don't you make c-client a shared
library?</strong></a></p>
<dl>
<dd>
All too often, shared libraries create far more problems than they
solve.
<p>Remember that you only gain the benefit of a shared library when
there are multiple applications which use that shared library. Even
without shared libraries, on most modern operating systems (and many
ancient ones too!) applications will share their text segments between
across multiple processes running the same application. This means that
if your system only runs one application (e.g. imapd) that uses the
c-client library, then you gain no benefit from making c-client a
shared library even if it has 100 imapd processes. You will, however
suffer added complexity.</p>
<p>If you have a server system that just runs imapd and ipop3d, then
making c-client a shared library will save just one copy of c-client no
matter how many IMAP/POP3 processes are running.</p>
<p>The problem with shared libraries is that you have to keep around a
copy of the library every time something changes in the library that
would affect the interface the library presents to the application. So,
you end up having many copies of the same shared library.</p>
<p>If you don't keep multiple copies of the shared library, then one of
two things happens. If there was proper versioning, then you'll get a
message such as "cannot open shared object file" or "minor versions
don't match" and the application won't run. Otherwise, the application
will run, but will fail in mysterious ways.</p>
<p>Several sites and third-party distributors have modified the
c-client makefile in order to make c-client be a shared library.
<em>When</em> (not <em>if</em>) a c-client based application fails in
mysterious ways because of a library compatibility problem, the result
is a bug report. A lot of time and effort ends up getting wasted
investigating such bug reports.</p>
<p>Memory is so cheap these days that it's not worth it. Human life is
too short to deal with shared library compatibility problems.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.4"><strong>6.4 Why don't you use iconv() for internationalization
support?</strong></a></p>
<dl>
<dd>iconv() is not ubiquitous enough.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.5"><strong>6.5 Why is the IMAP server connected to the home
directory by default?</strong></a></p>
<dl>
<dd>
The IMAP server has no way of knowing what you might call "mail" as
opposed to "some other file"; in fact, you can use IMAP to access any
file.
<p>The IMAP server also doesn't know whether your preferred
subdirectory for mailbox files is "mail/", ".mail/", "Mail/",
"Mailboxes/", or any of a zillion other possibilities. If one such name
were chosen, it would undoubtably anger the partisans of all the other
names.</p>
<p>It is possible to modify the software so that the default connected
directory is someplace else. Please read the file CONFIG for discussion
of this and other issues.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.6"><strong>6.6 I have a Windows system. Why isn't the server plug
and play for me?</strong></a></p>
<dl>
<dd>
There is no standard for how mail is stored on Windows; nor a single
standard SMTP server. The closest to either would be the SMTP server in
Microsoft's IIS.
<p>So there's no default by which to make assumptions. As the software
is set up, it assumes that the each user has an Windows login account
and private home directory, and that mail is stored on that home
directory as files in one of the popular UNIX formats. It also assumes
that there is some tool equivalent to inetd on UNIX that does the
TCP/IP listening and server startup.</p>
<p>Basically, unless you're an email software hacker, you probably want
to look elsewhere if you want IMAP/POP servers for Windows.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.7"><strong>6.7 I looked at the UNIX SSL code and saw that you have
the SSL data payload size set to 8192 bytes. SSL allows 16K; why aren't
you using the full size?</strong></a></p>
<dl>
<dd>
This is to avoid an interoperability problem with:
<ul>
<li>PC IMAP clients that use Microsoft's SChannel.DLL (SSPI) for SSL
support</li>
<li>Microsoft Exchange server (which also uses SChannel).</li>
</ul>
<p>SChannel has a bug that makes it think that the maximum SSL data
payload size is 16379 bytes -- 5 bytes too small. Thus, c-client has to
make sure that it never transmits full sized SSL packets.</p>
<p>The reason for using 8K (as opposed to, say, 16379 bytes, or 15K,
or...) is that it corresponds with the TCP buffer size that the
software uses elsewhere for input; there's a slight performance benefit
to having the two sizes correspond or at least be a multiple of each
other. Also, it keeps the size as a power of two, which might be
significant on some platforms.</p>
<p>There wasn't a significant difference that we could measure between
8K and 15K.</p>
<p>Microsoft has developed a hotfix for this bug. Look up MSKB article
number 300562. Contrary to the article text which implies that this is
a Pine issue, this bug also affects Microsoft Exchange server with
<em>any</em> client that transmits full-sized SSL payloads.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.8"><strong>6.8 Why is an mh format INBOX called #mhinbox instead
of just INBOX?</strong></a></p>
<dl>
<dd>
It's a long story. In brief, the mh format driver is less functional
than any of the other drivers. It turned out that there were some users
(including high-level administrators) who tried mh years ago and no
longer use it, but still had an mh profile left behind.
<p>When the mh driver used INBOX, it would see the mh profile, and
proceed to move the user's INBOX into the mh format INBOX. This caused
considerable confusion as some things stopped working.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.9"><strong>6.9 Why don't you support the maildir
format?</strong></a></p>
<dl>
<dd>
It is technically difficult to support maildir in IMAP while
maintaining acceptable performance, robustness, following the
requirements of the IMAP protocol specification, and following the
requirements of maildir.
<p>No one has succeeded in accomplishing all four together. The various
maildir drivers offered as patches all have these problems. The problem
is exacerbated because this implementation supports multiple formats;
consequently this implementation can't make any performance shortcuts
by assuming that all the world is maildir.</p>
<p>We can't do a better job than the maildir fan community has done
with their maildir drivers. Similarly, if the maildir fan community
provides the maildir driver, they take on the responsibility for
answering maildir-specific support questions. This is as it should be,
and that is why maildir support is left to the maildir fan
community.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.10"><strong>6.10 Why don't you support the Cyrus
format?</strong></a></p>
<dl>
<dd>
There's no point to doing so. An implementation which supports multiple
formats will never do as well as one which is optimized to support one
single format.
<p>If you want to use Cyrus mailbox format, you should use the Cyrus
server, which is the native implementation of that format and is
specifically optimized for that format. That's also why Cyrus doesn't
implement any other format.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.11"><strong>6.11 Why is it creating extra forks on my SVR4
system?</strong></a></p>
<dl>
<dd>
This is because your system only has fcntl() style locking and not
flock() style locking. fcntl() locking has a design flaw that causes a
close() to release any locks made by that process on the file opened on
that file descriptor, even if the lock was made on a different file
descriptor.
<p>This design flaw causes unexpected loss of lock, and consequent
mailbox corruption. The workaround is to do certain "dangerous
operations" in another fork, thus avoiding doing a close() in the
vulnerable fork.</p>
<p>The best way to solve this problem is to upgrade your SVR4 (Solaris,
AIX, HP-UX, SGI) or OSF/1 system to a more advanced operating system,
such as Linux or BSD. These more advanced operating systems have
fcntl() locking for compatibility with SVR4, but also have flock()
locking.</p>
<p>Beware of certain SVR4 systems, such as AIX, which have an "flock()"
function in their C library that is just a jacket that does an fcntl()
lock. This is not a true flock(), and has the same design flaw as
fcntl().</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.12"><strong>6.12 Why are you so fussy about the date/time format in
the internal <code>"From&nbsp;"</code> line in traditional UNIX mailbox
files? My other mail program just considers every line that starts with
<code>"From&nbsp;"</code> to be the start of the message.</strong></a></p>
<dl>
<dd>
You just answered your own question. If any line that starts with
<code>"From&nbsp;"</code> is treated as the start of a message, then
every message text line which starts with <code>"From&nbsp;"</code> has
to be quoted (typically by prefixing a "&gt;" character). People
complain about this -- "why did a &gt; get stuck in my message?"
<p>So, good mail reading software only considers a line to be a
<code>"From&nbsp;"</code> line if it follows the actual specification
for a "From&nbsp;" line. This means, among other things, that the day of
week is fixed-format: <code>"May&nbsp;14"</code>, but
<code>"May&nbsp;&nbsp;7"</code> (note the extra space) as opposed to
<code>"May&nbsp;7"</code>. ctime() format for the date is the most
common, although POSIX also allows a numeric timezone after the
year. For compatibility with ancient software, the seconds are optional,
the timezone may appear before the year, the old 3-letter timezones are
also permitted, and "remote from xxx" may appear after the whole
thing.</p>
<p>Unfortunately, some software written by novices use other formats.
The most common error is to have a variable-width day of month, perhaps
in the erroneous belief that RFC 2822 (or RFC 822) defines the format of
the date/time in the <code>"From&nbsp;"</code> line (it doesn't; no RFC
describes internal formats). I've seen a few other goofs, such as a
single-digit second, but these are less common.</p>
<p>If you are writing your own software that writes mailbox files, and
you really aren't all that savvy with all the ins and outs and ancient
history, you should seriously consider using the c-client library (e.g.
routine mail_append()) instead of doing the file writes yourself. If
you must do it yourself, use ctime(), as in:</p>
<pre>
fprintf (mbx,"From %s@%h %s",user,host,ctime (time (0)));
</pre>rather than try to figure out a good format yourself. ctime() is the
most traditional format and nobody will flame you for using it.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.13"><strong>6.13 Why is traditional UNIX format the default
format?</strong></a></p>
<dl>
<dd>Compatibility with the past 30 or so years of UNIX history. This
server is the only one that completely interoperates with legacy UNIX
mail tools.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.14"><strong>6.14 Why do you write this "DON'T DELETE THIS MESSAGE
-- FOLDER INTERNAL DATA" message at the start of traditional UNIX and
MMDF format mailboxes?</strong></a></p>
<dl>
<dd>
This pseudo-message serves two purposes.
<p>First, it establishes the mailbox format even when the mailbox has
no messages. Otherwise, a mailbox with no messages is a zero-byte file,
which could be one of several formats.</p>
<p>Second, it holds mailbox metadata used by IMAP: the UID validity,
the last assigned UID, and mailbox keywords. Without this metadata,
which must be preserved even when the mailbox has no messages, the
traditional UNIX format wouldn't be able to support the full
capabilities of IMAP.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.15"><strong>6.15 Why don't you stash the mailbox metadata in the
first real message of the mailbox instead of writing this fake FOLDER
INTERNAL DATA message?</strong></a></p>
<dl>
<dd>
In fact, that is what is done if the mailbox is non-empty and does not
already have a FOLDER INTERNAL DATA message.
<p>One problem with doing that is that if some external program removes
the first message, the metadata is lost and must be recreated, thus
losing any prior UID or keyword list status that IMAP clients may
depend upon.</p>
<p>Another problem is that this doesn't help if the last message is
deleted. This will result in an empty mailbox, and the necessity to
create a FOLDER INTERNAL DATA message.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.16"><strong>6.16 Why aren't "dual-use" mailboxes the
default?</strong></a></p>
<dl>
<dd>Compatibility with the past 30 or so years of UNIX history, not to
mention compatibility with user expectations when using shell tools.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.17"><strong>6.17 Why do you use ucbcc to build on
Solaris?</strong></a></p>
<dl>
<dd>
It is a long, long story about why cc is set to ucbcc. You need to
invoke the C compiler so that it links with the SVR4 libraries and not
the BSD libraries, otherwise readdir() will return the wrong
information.
<p>Of all the names in the most common path, ucbcc is the only name to
be found (on /usr/ccs/bin) that points to a suitable compiler. cc is
likely to be /usr/ucb/cc which is absolutely not the compiler that you
want. The real SVR4 cc is probably something like /opt/SUNWspro/bin/cc
which is rarely in anyone's path by default.</p>
<p>ucbcc is probably a link to acc, e.g. /opt/SUNWspro/SC4.0/bin/acc,
and is the UCB C compiler using the SVR4 libraries.</p>
<p>If ucbcc isn't on your system, then punt on the SUN C compiler and
use gcc instead (the gso port instead of the sol port).</p>
<p>If, in spite of all the above warnings, you choose to change "ucbcc"
to "cc", you will probably find that the -O2 needs to be changed to -O.
If you don't get any error messages with -O2, that's a pretty good
indicator that you goofed and are running the compiler that will link
with the BSD libraries.</p>
<p>To recap:</p>
<ul>
<li>The sol port is designed to be built using the UCB compiler using
the SVR4 libraries. This compiler is "ucbcc", which is lunk to acc.
You use -O2 as one of the CFLAGS.</li>
<li>If you build the sol port with the UCB compiler using the BSD
libraries, you will get no error messages but you will get bad
binaries (the most obvious symptom is dropping the first two
characters return filenames from the imapd LIST command. This
compiler also uses -O2, and is very often what the user gets from
"cc". <strong>BEWARE</strong></li>
<li>If you build the sol port with the real SVR4 compiler, which is
often hidden away or unavailable on many systems, then you will get
errors from -O2 and you need to change that to -O. But you will get a
good binary. However, you should try it with -O2 first, to make sure
that you got this compiler and not the UCB compiler using BSD
libraries.</li>
</ul>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.18"><strong>6.18 Why should I care about some old system with BSD
libraries? cc is the right thing on my Solaris system!</strong></a></p>
<dl>
<dd>
Because there still are sites that use such systems. On those systems,
the assumption that "cc" does the right thing will lead to corrupt
binaries with no error message or other warning that anything is amiss.
<p>Too many sites have fallen victim to this problem.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.19"><strong>6.19 Why do you insist upon writing .lock files in the
spool directory?</strong></a></p>
<dl>
<dd>Compatibility with the past 30 years of UNIX software which deals
with the spool directory, especially software which delivers mail.
Otherwise, it is possible to lose mail.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="6.20"><strong>6.20 Why should I care about compatibility with the
past?</strong></a></p>
<dl>
<dd>This is one of those questions in which the answer never convinces
those who ask it. Somehow, everybody who ever asks this question ends up
answering it for themselves as they get older, with the very answer that
they rejected years earlier.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="problems">7. Problems and Annoyances</a></h2>
<hr>
<p><a name="7.1"><strong>7.1 Help! My INBOX is empty! What happened to my
messages?</strong></a></p>
<dl>
<dd>
If you are seeing "0 messages" when you open INBOX and you know you
have messages there (and perhaps have looked at your mail spool file
and see that messages are there), then probably there is something
wrong with the very first line of your mail spool file. Make sure that
the first five bytes of the file are "From ", followed by an email
address and a date/time in ctime() format, e.g.:
<pre>
From fred@foo.bar Mon May 7 20:54:30 2001
</pre>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.2"><strong>7.2 Help! All my messages in a non-INBOX mailbox have
been concatenated into one message which claims to be from me and has a
subject of the file name of the mailbox! What's going
on?</strong></a></p>
<dl>
<dd>
Something wrong with the very first line of the mailbox. Make sure that
the first five bytes of the file are "From ", followed by an email
address and a date/time in ctime() format, e.g.:
<pre>
From fred@foo.bar Mon May 7 20:54:30 2001
</pre>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.3"><strong>7.3 Why do I get the message:</strong> <tt>CREATE
failed: Can't create mailbox node xxxxxxxxx: File exists</tt>
<strong>and how do I fix it?</strong></a></p>
<dl>
<dd>See the answer to the <a href="#1.8">Are hierarchical mailboxes
supported?</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.4"><strong>7.4 Why can't I log in to the server? The user name and
password are right!</strong></a></p>
<dl>
<dd>
There are a myriad number of possible answers to this question. The
only way to say for sure what is wrong is run the server under a
debugger such as gdb while root (yes, you must be root) with a
breakpoint at routines checkpw() and loginpw(), then single-step until
you see which test rejected you. The server isn't going to give any
error messages other than "login failed" in the name of not giving out
any unnecessary information to unauthorized individuals.
<p>Here are some of the more common reasons why login may fail:</p>
<ul>
<li>You didn't really give the correct user name and/or
password.</li>
<li>Your client doesn't send the LOGIN command correctly; for
example, IMAP2 clients won't send a password containing a "*"
correctly to an IMAP4 server.</li>
<li>If you have set up a CRAM-MD5 database, remember that the
password used is the one in the CRAM-MD5 database, and furthermore
that there must also be an entry in /etc/passwd (but the /etc/passwd
password is not used).</li>
<li>If you are using PAM, have you created a service file for the
server in /etc/pam.d?</li>
<li>If you are using shadow passwords, have you used an appropriate
port when building? In particular, note that "lnx" is for Linux
systems without shadow passwords; you probably want "slx" or "lnp"
instead.</li>
<li>If your system has account or password expirations, check to see
that the expiration date hasn't passed.</li>
<li>You can't log in as root or any other UID 0 user. This is for
your own safety, not to mention the fact that the servers use UID 0
as meaning "not logged in".</li>
</ul>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.5"><strong>7.5 Help! My load average is soaring and I see hundreds
of POP and IMAP servers, many logged in as the same
user!</strong></a></p>
<dl>
<dd>
Certain inferior losing GUI mail reading programs have a "synchronize
all mailboxes at startup" (IMAP) or "check for new mail every second"
(POP) feature which causes a rapid and unchecked spawning of servers.
<p>This is not a problem in the server; the client is really asking for
all those server sessions. Unfortunately, there isn't much that the POP
and IMAP servers can do about it; they don't spawned themselves.</p>
<p>Some sites have added code to record the number of server sessions
spawned per user per hour, and disable login for a user who has
exceeded a predetermined rate. This doesn't stop the servers from being
spawned; it just means that a server session will commit suicide a bit
faster.</p>
<p>Another possibility is to detect excessive server spawning activity
at the level where the server is spawned, which would be inetd or
possibly tcpd. The problem here is that this is a hard time to
quantify. 50 sessions in a minute from a multi-user timesharing system
may be perfectly alright, whereas 10 sessions a minute from a PC may be
too much.</p>
<p>The real solution is to fix the client configuration, by disabling
those evil features. Also tell the vendors of those clients how you
feel about distributing denial-of-service attack tools in the guise of
mail reading programs.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.6"><strong>7.6 Why does mail disappear even though I set "keep
mail on server"?</strong></a><br>
<a name="7.7"><strong>7.7 Why do I get the message</strong> <tt>Moved #####
bytes of new mail to /home/user/mbox from /var/spool/mail/user</tt>
<strong>and why did this happen?</strong></a></p>
<dl>
<dd>
This is probably caused by the mbox driver. If the file "mbox" exists
on the user's home directory and is in UNIX mailbox format, then when
INBOX is opened this file will be selected as INBOX instead of the mail
spool file. Messages will be automatically transferred from the mail
spool file into the mbox file.
<p>To disable this behavior, delete "mbox" from the EXTRADRIVERS list
in the top-level Makefile and rebuild. Note that if you do this, users
won't be able to access the messages that have already been moved to
mbox unless they open mbox instead of INBOX.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.8"><strong>7.8 Why isn't it showing the local host name as a
fully-qualified domain name?</strong></a><br>
<a name="7.9"><strong>7.9 Why is the local host name in the
From/Sender/Message-ID headers of outgoing mail not coming out as a
fully-qualified domain name?</strong></a></p>
<dl>
<dd>
Your UNIX system is misconfigured. The entry for your system in
/etc/hosts must have the fully-qualified domain name first, e.g.
<pre>
105.69.1.234 myserver.example.com myserver
</pre>
<p>A common mistake of novice system administrators is to have the
short name first, e.g.</p>
<pre>
105.69.1.234 myserver myserver.example.com
</pre>
<p>or to omit the fully qualified domain name entirely, e.g.</p>
<pre>
105.69.1.234 myserver
</pre>
<p>The result of this is that when the IMAP toolkit does a
gethostbyname() call to get the fully-qualified domain name, it would
get "myserver" instead of "myserver.example.com".</p>
<p>On some systems, a configuration file (typically named
/etc/svc.conf, /etc/netsvc.conf, or /etc/nsswitch.conf) can be used to
configure the system to use the domain name system (DNS) instead of
/etc/hosts, so it doesn't matter if /etc/hosts is misconfigured.</p>
<p>Check the man pages for gethostbyname, hosts, svc, and/or netsvc for
more information.</p>
<p>Unfortunately, certain vendors, most notably SUN, have failed to
make this clear in their documentation. Most of SUN's documentation
assumes a corporate network that is not connected to the Internet.</p>
<p>net.folklore once (late 1980s) held that the proper procedure was to
append the results of getdomainname() to the name returned by
gethostname(), and some versions of sendmail configuration files were
distributed that did this. This was incorrect; the string returned from
getdomainname() is the Yellow Pages (a.k.a NIS) domain name, which is a
completely different (albeit unfortunately named) entity from an
Internet domain. These were often fortuitously the same string, except
when they weren't. Frequently, this would result in host names with
spuriously doubled domain names, e.g.</p>
<pre>
myserver.example.com.example.com
</pre>
<p>This practice has been thoroughly discredited for many years, but
folklore dies hard.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.10"><strong>7.10 What does the message:</strong> <tt>Mailbox
vulnerable - directory /var/spool/mail must have 1777 protection</tt>
<strong>mean? How can I fix this?</strong></a></p>
<dl>
<dd>
In order to update a mailbox in the default UNIX format, it is
necessary to create a lock file to prevent the mailer from delivering
mail while an update is in progress. Some systems use a directory
protection of 775, requiring that all mail handling programs be setgid
mail; or of 755, requiring that all mail handling programs be setuid
root.
<p>The IMAP toolkit does not run with any special privileges, and I
plan to keep it that way. It is antithetical to the concept of a
toolkit if users can't write their own programs to use it. Also, I've
had enough bad experiences with security bugs while running privileged;
the IMAP and POP servers have to be root when not logged in, in order
to be able to log themselves in. I don't want to go any deeper down
that slippery slope.</p>
<p>Directory protection 1777 is secure enough on most well-managed
systems. If you can't trust your users with a 1777 mail spool (petty
harassment is about the limit of the abuse exposure), then you have
much worse problems then that.</p>
<p>If you absolutely insist upon requiring privileges to create a lock
file, external file locking can be done via a setgid mail program named
/etc/mlock (this is defined by LOCKPGM in the c-client Makefile). If
the toolkit is unable to create a &lt;...mailbox...&gt;.lock file in
the directory by itself, it will try to call mlock to do it. I do not
recommend doing this for performance reasons.</p>
<p>A sample mlock program is included as part of imap-2007. We have
tried to make this sample program secure, but it has not been
thoroughly audited.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.11"><strong>7.11 What does the message:</strong> <tt>Mailbox is
open by another process, access is readonly</tt> <strong>mean? How do I
fix this?</strong></a></p>
<dl>
<dd>
A problem occurred in applying a lock to a /tmp lock file. Either some
other program has the mailbox open and won't relenquish it, or
something is wrong with the protection of /tmp or the lock.
<p>Make sure that the /tmp directory is protected 1777. Some security
scripts incorrectly set the protection of the /tmp directory to 775,
which disables /tmp for all non-privileged programs.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.12"><strong>7.12 What does the message:</strong> <tt>Can't get
write access to mailbox, access is readonly</tt>
<strong>mean?</strong></a></p>
<dl>
<dd>The mailbox file is write-protected against you.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.13"><strong>7.13 I set my POP3 client to "delete messages from
server" but they never get deleted. What is wrong?</strong></a></p>
<dl>
<dd>
Make sure that your mailbox is not read-only: that the mailbox is owned
by you and write enabled (protection 0600), and that the /tmp directory
is longer world-writeable. /tmp must be world-writeable because lots of
applications use it for scratch space. To fix this, do
<pre>
chmod 1777 /tmp
</pre>as root.
<p>Make sure that your POP3 client issues a QUIT command when it
finishes. The POP3 protocol specifies that deletions are discarded
unless a proper QUIT is done.</p>
<p>Make sure that you are not opening multiple POP3 sessions to the
same mailbox. It is a requirement of the POP3 protocol than only one
POP3 session be in effect to a mailbox at a time, however some,
poorly-written POP3 clients violate this. Also, some background "check
for new mail" tasks also cause a violation. See the answer to the
<a href="#7.19">What does the syslog message: Killed (lost mailbox
lock) user=... host=... mean?</a> question for more details.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.14"><strong>7.14 What do messages such as:</strong></a></p>
<pre>
Message ... UID ... already has UID ...
Message ... UID ... less than ...
Message ... UID ... greater than last ...
Invalid UID ... in message ..., rebuilding UIDs
</pre>
<p><strong>mean?</strong></p>
<dl>
<dd>
Something happened to corrupt the unique identifier regime in the
mailbox. In traditional UNIX-format mailboxes, this can happen if the
user deleted the "DO NOT DELETE" internal message.
<p>This problem is relatively harmless; a new valid unique identifier
regime will be created. The main effect is that any references to the
old UIDs will no longer be useful.</p>
<p>So, unless it is a chronic problem or you feel like debugging, you
can safely ignore these messages.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.15"><strong>7.15 What do the error messages:</strong></a></p>
<pre>
Unable to read internal header at ...
Unable to find CRLF at ...
Unable to parse internal header at ...
Unable to parse message date at ...
Unable to parse message flags at ...
Unable to parse message UID at ...
Unable to parse message size at ...
Last message (at ... ) runs past end of file ...
</pre>
<p><strong>mean? I am using mbx format.</strong></p>
<dl>
<dd>
The mbx-format mailbox is corrupted and needs to be repaired.
<p>You should make an effort to find out why the corruption happened.
Was there an obvious system problem (crash or disk failure)? Did the
user accidentally access the file via NFS? Mailboxes don't get
corrupted by themselves; something caused the problem.</p>
<p>Some people have developed automated scripts, but if you're
comfortable using emacs it's pretty easy to fix it manually. Do
<em>not</em> use vi or any other editor unless you are certain that
editor can handle binary!!!</p>
<p>If you are not comfortable with emacs, or if the file is too large
to read with emacs, see the "step-by-step" technique later on for
another way of doing it.</p>
<p>After the word "at" in the error message is the byte position it got
to when it got unhappy with the file, e.g. if you see:</p>
<pre>
Unable to parse internal header at 43921: ne bombastic blurdybloop
</pre>The problem occurs at the 43,931 byte in the file. That's the point you
need to fix. c-client is expecting an internal header at that byte number,
looking something like:
<pre>
6-Jan-1998 17:42:24 -0800,1045;000000100001-00000001
</pre>The format of this internal line is:
<pre>
dd-mmm-yyyy hh:mm:ss +zzzz,ssss;ffffffffFFFF-UUUUUUUU
</pre>The only thing that is variable is the "ssss" field, it can be as many
digits as needed. All other fields (inluding the "dd") are fixed width. So,
the easiest thing to do is to look forward in the file for the next internal
header, and delete everything from the error point to that internal header.
<p>Here's what to do if you want to be smarter and do a little bit more
work. Generally, you're in the middle of a message, and there's nothing
wrong with that message. The problem happened in the *previous*
message. So, search back to the previous internal header. Now, remember
that "ssss" field? That's the size of that message.</p>
<p>Mark where you are in the file, move the cursor to the line after
the internal header, and skip that many bytes ("ssss") forward. If
you're at the point of the error in the file, then that message is
corrupt. If you're at a different point, then perhaps the previous
message is corrupt and has a too long size count that "ate" into this
message.</p>
<p>Basically, what you need to do is make sure that all those size
counts are right, and that moving "ssss" bytes from the line after the
internal header will land you at another internal header.</p>
<p>Usually, once you know what you're looking at, it's pretty easy to
work out the corruption, and the best remedial action. Repair scripts
will make the problem go away but may not always do the smartest/best
salvage of the user's data. Manual repair is more flexible and usually
preferable.</p>
<p>Here is a step-by-step technique for fixing corrupt mbx files that's
a bit cruder than the procedure outlined above, but works for any size
file.</p>
<p>In this example, suppose that the corrupt file is INBOX, the error
message is</p>
<pre>
Unable to find CRLF at 132551754
</pre>and the size of the INBOX file is 132867870 bytes.
<p>The first step is to split the mailbox file at the point of the
error:</p>
<ul>
<li>Rename the INBOX file to some other name, such as INBOX.bad.</li>
<li>Copy the first 132,551,754 bytes of INBOX.bad to another file,
such as INBOX.new.</li>
<li>Extract the trailing 316,116 bytes (132867870-132551754) of
INBOX.bad into another file, such as INBOX.tail.</li>
<li>You no longer need INBOX.bad. Delete it.</li>
</ul>In other words, use the number from the "Unable to find CRLF at"
as the point to split INBOX into two new files, INBOX.new and
INBOX.tail.
<p>Now, remove the erroneous data:</p>
<ul>
<li>Verify that you can open INBOX.new in IMAP or Pine.</li>
<li>The last message of INBOX.new is probably corrupted. Copy it to
another file, such as badmsg.1, then delete and expunge that last
message from INBOX.new</li>
<li>Locate the first occurance of text in INBOX.tail which looks like
an internal header, as described above.</li>
<li>Remove all the text which occurs prior to that point, and place
it into another file, such as badmsg.2. Note that in the case of a
single digit date, there is a leading space which must not be removed
(e.g. " 6-Nov-2001" not "6-Nov-2001").</li>
</ul>
<p>Reassemble the mailbox:</p>
<ul>
<li>Append INBOX.tail to INBOX.new.</li>
<li>You no longer need INBOX.tail. Delete it.</li>
<li>Verify that you can open INBOX.new in IMAP or Pine.</li>
</ul>
<p>Reinstall INBOX.new as INBOX:</p>
<ul>
<li>Check to see if you have received any new messages while
repairing INBOX.</li>
<li>If you haven't received any new messages while repairing INBOX,
just rename INBOX.new to INBOX.</li>
<li>If you have received new messages, be sure to copy the new
messages from INBOX to INBOX.new before doing the rename.</li>
</ul>
<p>You now have a working INBOX, as well as two files with corrupted
data (badmsg.1 and badmsg.2). There may be some useful data in the two
badmsg files that you might want to try salvaging; otherwise you can
delete the two badmsg files.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.16"><strong>7.16 What do the syslog messages:</strong></a></p>
<pre>
imap/tcp server failing (looping)
pop3/tcp server failing (looping)
</pre>
<p><strong>mean? When it happens, the listed service shuts down. How can I
fix this?</strong></p>
<dl>
<dd>
The error message "server failing (looping), service terminated" is not
from either the IMAP or POP servers. Instead, it comes from inetd, the
daemon which listens for TCP connections to a number of servers,
including the IMAP and POP servers.
<p>inetd has a limit of 40 new server sessions per minute for any
particular service. If more than 40 sessions are initiated in a minute,
inetd will issue the "failing (looping), service terminated" message
and shut down the service for 10 minutes. inetd does this to prevent
system resource consumption by a client which is spawning infinite
numbers of servers. It should be noted that this is a denial of
service; however for some systems the alternative is a crash which
would be a worse denial of service!</p>
<p>For larger server systems, the limit of 40 is much too low. The
limit was established many years ago when a system typically only ran a
few dozen servers.</p>
<p>On some versions of inetd, such as the one distributed with most
versions of Linux, you can modify the <strong>/etc/inetd.conf</strong>
file to have a larger number of servers by appending a period followed
by a number after the <strong>nowait</strong> word for the server
entry. For example, if your existing /etc/inetd.conf line reads:</p>
<pre>
imap stream tcp nowait root /usr/etc/imapd imapd
</pre>try changing it to be:
<pre>
imap stream tcp nowait.100 root /usr/etc/imapd imapd
</pre>Another example (using TCP wrappers):
<pre>
imap stream tcp nowait root /usr/sbin/tcpd imapd
</pre>try changing it to be:
<pre>
imap stream tcp nowait.100 root /usr/sbin/tcpd imapd
</pre>to increase the limit to 100 sessions/minute.
<p>Before making this change, please read the information in "man
inetd" to determine whether or not your inetd has this feature. If it
does not, and you make this change, the likely outcome is that you will
disable IMAP service entirely.</p>
<p>Another way to fix this problem is to edit the inetd.c source code
(provided by your UNIX system vendor) to set higher limits, rebuild
inetd, install the new binary, and reboot your system. This should only
be done by a UNIX system expert. In the inetd.c source code, the limits
<strong>TOOMANY</strong> (normally 40) is the maximum number of new
server sessions permitted per minute, and <strong>RETRYTIME</strong>
(normally 600) is the number of seconds inetd will shut down the server
after it exceeds TOOMANY.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.17"><strong>7.17 What does the syslog message:</strong>
<tt>Mailbox lock file /tmp/.600.1df3 open failure: Permission
denied</tt> <strong>mean?</strong></a></p>
<dl>
<dd>
This usually means that some "helpful" security script person has
protected /tmp so that it is no longer world-writeable. /tmp must be
world-writeable because lots of applications use it for scratch space.
To fix this, do
<pre>
chmod 1777 /tmp
</pre>as root.
<p>If that isn't the answer, check the protection of the named file. If
it is something other than 666, then either someone is hacking or some
"helpful" person modified the code to have a different default lock
file protection.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.18"><strong>7.18 What do the syslog messages:</strong></a></p>
<pre>
Command stream end of file, while reading line user=... host=...
Command stream end of file, while reading char user=... host=...
Command stream end of file, while writing text user=... host=...
</pre>
<p><strong>mean?</strong></p>
<dl>
<dd>
This message occurs when the session is disconnected without a proper
LOGOUT (IMAP) or QUIT (POP) command being received by the server first.
<p>In many cases, this is perfectly normal; many client implementations
are impolite and do this. Some programmers think this sort of rudeness
is "more efficient".</p>
<p>The condition could, however, indicate a client or network
connectivity problem. The server has no way of knowing whether there's
a problem or just a rude client, so it issues this message instead of a
Logout.</p>
<p>Certain inferior losing clients disconnect abruptly after a failed
login, and instead of saying that the login failed, just say that they
can't access the mailbox. They then complain to the system manager, who
looks in the syslog and finds this message. Not very helpful, eh? See
the answer to the <a href="#7.4">Why can't I log in to the server? The
user name and password are right!</a> question.</p>
<p>If the user isn't reporting a problem, you can probably ignore this
message.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.19"><strong>7.19 Why did my POP or IMAP session suddenly
disconnect? The syslog has the message:</strong> <tt>Killed (lost
mailbox lock) user=... host=...</tt></a></p>
<dl>
<dd>
This message only happens when either the traditional UNIX mailbox
format or MMDF format is in use. This format only allows one session to
have the mailbox open read/write at a time.
<p>The servers assume that if a second session attempts to open the
mailbox, that means that the first session is probably owned by an
abandoned client. The common scenario here is a user who leaves his
client running at the office, and then tries to read his mail from
home. Through an internal mechanism called <em>kiss of death</em>, the
second session requests the first session to kill itself. When the
first session receives the "kiss of death", it issues the "Killed (lost
mailbox lock)" syslog message and terminates. The second session then
seizes read/write access, and becomes the new "first" session.</p>
<p>Certain poorly-designed clients routinely open multiple sessions to
the same mailbox; the users of those clients tend to get this message a
lot.</p>
<p>Another cause of this message is a background "check for new mail"
task which does its work by opening a POP session to server every few
seconds. They do this because POP doesn't have a way to announce new
mail.</p>
<p>The solution to both situations is to replace the client with a good
online IMAP client such as Pine. Life is too short to waste on POP
clients and poorly-designed IMAP clients.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.20"><strong>7.20 Why does my IMAP client show all the files on the
system, recursively from the UNIX root directory?</strong></a><br>
<a name="7.21"><strong>7.21 Why does my IMAP client show all of my files,
recursively from my UNIX home directory?</strong></a></p>
<dl>
<dd>
A well-written client should only show one level of hierarchy and then
stop, awaiting explicit user action before going lower. However, some
poorly-designed clients will recursively list all files, which may be a
very long list (especially if you have symbolic links to directories
that create a loop in the filesystem graph!).
<p>This behavior has also been observed in some third-party c-client
drivers, including maildir drivers. Consequently, this problem has even
been observed in Pine. It is important to understand that this is not a
problem in Pine or c-client; it is a problem in the third-party driver.
A Pine built without that third-party driver will not have this
problem.</p>
<p>See also the answer to <a href="#7.73">Why does my IMAP client show
all my files in my home directory?</a></p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.22"><strong>7.22 Why does my IMAP client show that I have
mailboxes named "#mhinbox", "#mh", "#shared", "#ftp", "#news", and
"#public"?</strong></a></p>
<dl>
<dd>
These are IMAP namespace names. They represent other hierarchies in
which messages may exist. These hierarchies may not necessarily exist
on a server, but the namespace name is still in the namespace list in
order to mark it as reserved.
<p>A few poorly-designed clients display all namespace names as if they
were top-level mailboxes in a user's list of mailboxes, whether or not
they actually exist. This is a flaw in those clients.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.23"><strong>7.23 Why does my IMAP client show all my files in my
home directory?</strong></a></p>
<dl>
<dd>
As distributed, the IMAP server is connected to your home directory by
default. It has no way of knowing what you might call "mail" as opposed
to "some other file"; in fact, you can use IMAP to access any file.
<p>Most clients have an option to configure your connected directory on
the IMAP server. For example, in Pine you can specify this as the
"Path" in your folder-collection, e.g.</p>
<pre>
Nickname : Secondary Folders
Server : imap.example.com
Path : mail/
View :
</pre>In this example, the user is connected to the "mail" subdirectory of
his home directory.
<p>Other servers call this the "folder prefix" or similar term.</p>
<p>It is possible to modify the IMAP server so that all users are
automatically connected to some other directory, e.g. a subdirectory of
the user's home directory. Read the file CONFIG for more details.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.24"><strong>7.24 Why is there a long delay before I get connected
to the IMAP or POP server, no matter what client I use?</strong></a></p>
<dl>
<dd>
There are two common occurances of this problem:
<ul>
<li>You are running a system (e.g. certain versions of Linux) which
by default attempts to connect to an "IDENT" protocol (port 113)
server on your client. However, a firewall or NAT box is blocking
connections to that port, so the connection attempt times out.
<p>The IDENT protocol is a well-known bad idea that does not
deliver any real security but causes incredible problems. The idea
is that this will give the server a record of the user name, or at
least what some program listening on port 113 says is the user
name. So, if somebody coming from port nnnnn on a system does
something bad, IDENT may give you the userid of the bad guy.</p>
<p>The problem is, IDENT is only meaningful on a timesharing system
which has an administrator who is privileged and users who are not.
It is of no value on a personal system which has no separate
concept of "system administrator" vs. "unprivileged user".</p>
<p>On either type of system, security-minded people either turn
IDENT off or replace it with an IDENT server that lies. Among other
things, IDENT gives spammers the ability to harvest email addresses
from anyone who connects to a web page.</p>
<p>This problem has been showing up quite frequently on systems
which use xinetd instead of inetd. Look for files named
/etc/xinetd.conf, /etc/xinetd.d/imapd, /etc/inetd.d/ipop2d, and
/etc/xinetd.d/ipop3d. In those files, look for lines containing
"USERID", e.g.</p>
<pre>
log_on_success += USERID
</pre>Hunt down such lines, and delete them ruthlessly from all files in
which they occur. Don't be shy about it.
</li>
<li>The DNS is taking a long time to do a reverse DNS (PTR record)
lookup of the IP address of your client. This is a problem in your
DNS, which either you or you ISP need to resolve. Ideally, the DNS
should return the client's name; but if it can't it should at least
return an error quickly.</li>
</ul>
<p>As you may have noticed, neither of these are actual problems in the
IMAP or POP servers; they are configuration issues with either your
system or your network infrastructure. If this is all new to you, run
(don't walk) to the nearest technical bookstore and get yourself a good
pedagogical text on system administration for the type of system you
are running.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.25"><strong>7.25 Why is there a long delay in Pine or any other
c-client based application call before I get connected to the IMAP
server? The hang seems to be in the c-client mail_open() call. I don't
have this problem with any other IMAP client. There is no delay
connecting to a POP3 or NNTP server with mail_open().</strong></a></p>
<dl>
<dd>
By default, the c-client library attempts to make a connection through
rsh (and ssh, if you enable that). If the command:
<pre>
rsh imapserver exec /etc/rimapd
</pre>(or ssh if that is enabled) returns with a "* PREAUTH" response, it
will use the resulting rsh session as the IMAP session and not require an
authentication step on the server.
<p>Unfortunately, rsh has a design error that treats "TCP connection
refused" as "temporary failure, try again"; it expects the "rsh not
allowed" case to be implemented as a successful connection followed by
an error message and close the connection.</p>
<p>It must be emphasized that this is a bug in rsh. It is <em>not</em>
a bug in the IMAP toolkit.</p>
<p>The use of rsh can be disabled in any the following ways:</p>
<ul>
<li>You can disable it for this particular session by either:
<ul>
<li>setting an explicit port number in the mailbox name, e.g.
<pre>
{imapserver.foo.com:143}INBOX
</pre>
</li>
<li>using SSL (the /ssl switch)</li>
</ul>
</li>
<li>You can disable rsh globally by setting the rsh timeout value to
0 with the call:
<pre>
mail_parameters (NIL,SET_RSHTIMEOUT,0);
</pre>
</li>
</ul>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.26"><strong>7.26 Why does a message sometimes get split into two
or more messages on my SUN system?</strong></a></p>
<dl>
<dd>
This is caused by an interaction of two independent design problems in
SUN mail software. The first problem is that the "forward message"
option in SUN's <em>mail tool</em> program includes the internal "From
" header line in the text that it forwarded. This internal header line
is specific to traditional UNIX mailbox files and is not suitable for
use in forwarded messages.
<p>The second problem is that the mail delivery agent assumes that mail
reading programs will not use the traditional UNIX mailbox format but
instead an incompatible variant that depends upon a
<em>Content-Length:</em> message header. Content-Length is widely
recognized to have been a terrible mistake, and is no longer
recommended for use in mail (it is used in other facilities that use
MIME).</p>
<p>One symptom of the problem is that under certain circumstances, a
message may get broken up into several messages. I'm also aware of
security bugs caused by programs that foolishly trust "Content-Length:"
headers with evil values.</p>
<p>To fix the mailer on your system, edit your sendmail.cf to change
the <strong>Mlocal</strong> line to have the <strong>-E</strong> flag.
A typical entry will lool like:</p>
<pre>
Mlocal, P=/usr/lib/mail.local, F=flsSDFMmnPE, S=10, R=20,
A=mail.local -d $u
</pre>This fix will also work around the problem with mail tool, because it
will insert a "&gt;" before the internal header line to prevent it from being
interpreted by mail reading software as an internal header line.
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.27"><strong>7.27 Why did my POP or IMAP session suddenly
disconnect? The syslog has the message:</strong></a></p>
<pre>
Autologout user=&lt;...my user name...&gt; host=&lt;...my client system...&gt;
</pre>
<dl>
<dd>
This is a problem in your client.
<p>In the case of IMAP, it failed to communicate with the IMAP server
for over 30 minutes; in the case of POP, it failed to communicate with
the POP server for over 10 minutes.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.28"><strong>7.28 What does the UNIX error message:</strong>
<tt>TLS/SSL failure: myserver: SSL negotiation failed</tt>
<strong>mean?</strong></a><br>
<a name="7.29"><strong>7.29 What does the PC error message:</strong>
<tt>TLS/SSL failure: myserver: Unexpected TCP input disconnect</tt>
<strong>mean?</strong></a></p>
<dl>
<dd>
This usually means that an attempt to negotiate TLS encryption via the
STARTTLS command failed, because the server advertises STARTTLS
functionality, but doesn't actually have it (e.g. because no
certificates are installed).
<p>Use the /notls option in the mailbox name to disable TLS
negotiation.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.30"><strong>7.30 What does the error message:</strong> <tt>TLS/SSL
failure: myserver: Server name does not match certificate</tt>
<strong>mean?</strong></a></p>
<dl>
<dd>
An SSL or TLS session encryption failed because the server name in the
server's certificate does not match the name that you gave it. This
could indicate that the server is not really the system you think that
it is, but can be also be called if you gave a nickname for the server
or name that was not fully-qualified. You must use the fully-qualified
domain name for the server in order to validate its certificate
<p>Use the /novalidate-cert option in the mailbox name to disable
validation of the certificate.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.31"><strong>7.31 What does the UNIX error message:</strong>
<tt>TLS/SSL failure: myserver: self-signed certificate</tt>
<strong>mean?</strong></a><br>
<a name="7.32"><strong>7.32 What does the PC error message:</strong>
<tt>TLS/SSL failure: myserver: Self-signed certificate or untrusted
authority</tt> <strong>mean?</strong></a></p>
<dl>
<dd>
An SSL or TLS session encryption failed because your server's
certificate is "self-signed"; that is, it is not signed by any
Certificate Authority (CA) and thus can not be validated. A CA-signed
certificate costs money, and some smaller sites either don't want to
pay for it or haven't gotten one yet. The bad part about this is that
this means there is no guarantee that the server is really the system
you think that it is.
<p>Use the /novalidate-cert option in the mailbox name to disable
validation of the certificate.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.33"><strong>7.33 What does the UNIX error message:</strong>
<tt>TLS/SSL failure: myserver: unable to get local issuer
certificate</tt> <strong>mean?</strong></a></p>
<dl>
<dd>
An SSL or TLS session encryption failed because your system does not
have the Certificate Authority (CA) certificates installed on OpenSSL's
certificates directory. On most systems, this directory is
/usr/local/ssl/certs). As a result, it is not possible to validate the
server's certificate.
<p>If CA certificates are properly installed, you should see
factory.pem and about a dozen other .pem names such as
thawteCb.pem.</p>
<p>As a workaround, you can use the /novalidate-cert option in the
mailbox name to disable validation of the certificate; however, note
that you are then vulnerable to various security attacks by bad
guys.</p>
<p>The correct fix is to copy all the files from the certs/ directory
in the OpenSSL distribution to the /usr/local/ssl/certs (or whatever)
directory. Note that you need to do this after building OpenSSL,
because the OpenSSL build creates a number of needed symbolic links.
For some bizarre reason, the OpenSSL "make install" doesn't do this for
you, so you must do it manually.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.34"><strong>7.34 Why does reading certain messages hang when using
Netscape? It works fine with Pine!</strong></a></p>
<dl>
<dd>
There are two possible causes.
<p>Check the mail syslog. If you see the message "Killed (lost mailbox
lock)" for the impacted user(s), read the FAQ entry regarding that
message.</p>
<p>Check the affected mailbox to see if there are embedded NUL
characters in the message. NULs in message texts are a technical
violation of both the message format and IMAP specifications. Most
clients don't care, but apparently Netscape does.</p>
<p>You can work around this by rebuilding imapd with the
<strong>NETSCAPE_BRAIN_DAMAGE</strong> option set (see
src/imapd/Makefile); this will cause imapd to convert all NULs to 0x80
characters. A better solution is to enable the feature in your MTA to
MIME-convert messages with binary content. See the documentation for
your MTA for how to do this.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.35"><strong>7.35 Why does Netscape say that there's a problem with
the IMAP server and that I should "Contact your mail server
administrator."?</strong></a></p>
<dl>
<dd>
Certain versions of Netscape do this when you click the Manage Mail
button, which uses an undocumented feature of Netscape's proprietary
IMAP server.
<p>You can work around this by rebuilding imapd with the
<strong>NETSCAPE_BRAIN_DAMAGE</strong> option set (see
src/imapd/Makefile) to a URL that points either to an alternative IMAP
client (e.g. Pine) or perhaps to a homebrew mail account management
page.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.36"><strong>7.36 Why is one user creating huge numbers of IMAP or
POP server sessions?</strong></a></p>
<dl>
<dd>The user is probably using Outlook Express, Eudora, or a similar
program. See the answer to the <a href="#7.5">Help! My load average is
soaring and I see hundreds of POP and IMAP servers, many logged in as the
same user!</a> question.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.37"><strong>7.37 Why don't I get any new mail notifications from
Outlook Express or Outlook after a while?</strong></a></p>
<dl>
<dd>
This is a known bug in Outlook Express. Microsoft is aware of the
problem and its cause. They have informed us that they do not have any
plans to fix it at the present time.
<p>The problem is also reported in Outlook 2000, but not verified.</p>
<p>Outlook Express uses the IMAP IDLE command to avoid having to "ping"
the server every few minutes for new mail. Unfortunately, Outlook
Express overlooks the part in the IDLE specification which requires
that a client terminate and restart the IDLE before the IMAP 30 minute
inactivity autologout timer triggers.</p>
<p>When this happens, Outlook Express displays "Not connected" at the
bottom of the window. Since it's no longer connected to the IMAP
server, it isn't going to notice any new mail.</p>
<p>As soon as the user does anything that would cause an IMAP
operation, Outlook Express will reconnect and new mail will flow again.
If the user does something that causes an IMAP operation at least every
29 minutes, the problem won't happen.</p>
<p>Modern versions of imapd attempt to work around the problem by
automatically reporting fake new mail after 29 minutes. This causes
Outlook Express to exit the IDLE state; as soon as this happens imapd
revokes the fake new mail. As long as this behavior isn't known to
cause problems with other clients, this workaround will remain in
imapd.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.38"><strong>7.38 Why don't I get any new mail notifications from
Entourage?</strong></a></p>
<dl>
<dd>
This is a known bug in Entourage.
<p>You built an older version of imapd with the
<strong>MICROSOFT_BRAIN_DAMAGE</strong> option set, in order to disable
support for the IDLE command. However, Entourage won't get new mail
unless IDLE command support exists.</p>
<p>Note: the MICROSOFT_BRAIN_DAMAGE option no longer exists in modern
versions, as the Outlook Express problem which it attempted to solve
has been worked around in another way.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.39"><strong>7.39 Why doesn't Entourage work at
all?</strong></a></p>
<dl>
<dd>
It's hard to know. Entourage breaks almost every rule in the book for
IMAP. It is highly instructive to do a packet trace on Entourage, as an
example of how <em>not</em> to use IMAP. It does things like STATUS
(MESSAGES) on the currently selected mailbox and re-fetching the same
static data over and over again.
<p>It seems that every time we understand what it is doing wrong in
Entourage and come up with a workaround, we learn about something else
that's broken.</p>
<p>Try building imapd with the <strong>ENTOURAGE_BRAIN_DAMAGE</strong>
option set, in order to disable the diagnostic that occurs when doing
STATUS on the currently selected mailbox.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.40"><strong>7.40 Why doesn't Netscape Notify (NSNOTIFY.EXE) work
at all?</strong></a></p>
<dl>
<dd>
This is a bug in NSNOTIFY; it doesn't handle unsolicited data from the
server correctly.
<p>Fortunately, there is no reason to use this program with IMAP;
NSNOTIFY is a polling program to let you know when new mail has
appeared in your maildrop. This is necessary with POP; but since IMAP
dynamically announces new mail in the session you're better off (and
will actually cause less load on the server!) keeping your mail reading
program's IMAP session open and let IMAP do the notifying for you.</p>
<p>Consequently, the recommended fix for the NSNOTIFY problem is to
delete the NSNOTIFY binary.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.41"><strong>7.41 Why can't I connect via SSL to Eudora? It says
the connection has been broken, and in the server syslogs I see "Command
stream end of file".</strong></a></p>
<dl>
<dd>There is a report that you can fix the problem by going into Eudora's
advanced network configuration menu and increasing the network buffer
size to 8192.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.42"><strong>7.42 Sheesh. Aren't there <em>any</em> good IMAP
clients out there?</strong></a></p>
<dl>
<dd>
Yes!
<p>Pine is a <em>wonderful</em> client. It's fast, it uses IMAP well,
and it generates text mail (life is too short to waste on HTML mail).
Also, there are some really wonderful things in progress in the Pine
world.</p>
<p>There are some good GUI clients out there, mostly from smaller
vendors. Without naming names, look for the vendors who are active in
the IMAP protocol development community, and their products.</p>
<p>Netscape, Eudora, and Outlook <em>can</em> be configured with enough
effort to be good citizens and work well for users, <em>but</em> they
can also be badly misconfigured, and often the misconfiguration is the
default.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.43"><strong>7.43 But wait! PC Pine (or other PC program build with
c-client) crashes with the message</strong> <tt>incomplete SecBuffer
exceeds maximum buffer size</tt> <strong>when I use SSL connections.
This is a bug in c-client, right?</strong></a></p>
<dl>
<dd>
It's a bug in the Microsoft SChannel.DLL, which implements SSL.
Microsoft admits it (albeit with an unstatement: "it's not fully RFC
compliant"). The problem is that SChannel indicates that the maximum
SSL packet data size is 5 bytes smaller than the actual maximum. Thus,
any IMAP server which transmits a maximum sized SSL packet will not
work with PC Pine or any other program which uses SChannel.
<p>It can take a while for the problem to show up. The client has to do
something that causes at least 16K of contiguous data. Many clients do
partial fetching, which tends to reduce the number of cases where this
can happen. However, <em>all</em> software which uses SChannel to
support SSL is affected by this bug.</p>
<p>This problem does not affect UNIX code, since OpenSSL is used on
UNIX.</p>
<p>This problem most recently showed up with the CommunigatePro IMAP
server. They have an update which trims down their maximum contiguous
data to less than 16K, in order to work around the problem.</p>
<p>This problem has also shown up with the Exchange IMAP server with
UNIX clients (including Pine built with an older version of c-client)
which sends full-sized 16K SSL packets. Modern c-client works around
the problem by trimming down its maximum outgoing SSL packet size to
8K.</p>
<p>Microsoft has developed a hotfix for this bug. Look up MSKB article
number 300562. Contrary to the article text which implies that this is
a Pine issue, this bug also affect Microsoft Exchange server with *any*
UNIX based client that transmits full-sized SSL payloads.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.44"><strong>7.44 My qpopper users keep on getting the DON'T DELETE
THIS MESSAGE -- FOLDER INTERNAL DATA if they also use Pine or IMAP. How
can I fix this?</strong></a></p>
<dl>
<dd>
This is an incompatibility between qpopper and the c-client library
used by Pine, imapd, and ipop[23]d.
<p>Assuming that you want to continue using qpopper, look into
qpopper's <strong>--enable-uw-kludge-flag</strong> configuration flag,
which is documented as "check for and hide UW 'Folder Internal Data'
messages".</p>
<p>The other alternative is to switch from qpopper to ipop3d.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.45"><strong>7.45 Help! I installed the servers but I can't connect
to them from my client!</strong></a></p>
<dl>
<dd>
Review the installation instructions carefully. Make sure that you have
not skipped any of the steps. Make sure that you have made the correct
entries in the configuration files; pay careful attention to the exact
spelling of the service names and the path names. Make sure as well
that you have properly restarted inetd.
<p>If you have a system with Yellow Pages/NIS such as Solaris, have you
updated the service names there as well as in /etc/services?</p>
<p>If you have a system with TCP wrappers, have you properly updated
the TCP wrapper files (e.g. /etc/hosts.allow and /etc/hosts.deny) for
the servers?</p>
<p>If you have a system which uses xinetd instead of inetd, have you
made sure that you have made the correct corresponding xinetd changes
for those services?</p>
<p>Try telneting to the server port (143 for IMAP, 110 for POP3). If
you get a "refused" error, that probably means that you don't have the
service set up in inetd.conf. If the connection opens and then closes
with no message, the service is set up, but either the path name of the
server binary in inetd.conf is wrong or your TCP wrappers are
configured to deny access.</p>
<p>If you don't know how to make the corresponding changes to these
files, seek the help of a local expert for your system.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.46"><strong>7.46 Why do I get the message</strong> <tt>Can not
authenticate to SMTP server: 421 SMTP connection went away!</tt>
<strong>and why did this happen? There was also something about</strong>
<tt>SECURITY PROBLEM: insecure server advertised AUTH=PLAIN</tt></a></p>
<dl>
<dd>
Some versions of qmail, including that running on mail.smtp.yahoo.com,
disconnect the SMTP session if you fail to authenticate prior to
attempting to transmit mail. An attempt to authenticate was made, but
it failed because the server had already disconnected.
<p>To work around this, you need to specify /user=... in the host name
specification.</p>
<p>The SECURITY PROBLEM came about because the server advertised the
AUTH=PLAIN SASL authentication mechanism outside of a TLS-encrypted
session, in violation of RFC 4616. This message is just a warning, and
in fact occurred after the server had disconnected.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.47"><strong>7.47 Why do I get the message</strong> <tt>SMTP
Authentication cancelled</tt> <strong>and why did this happen? There was
also something about</strong> <tt>SECURITY PROBLEM: insecure server
advertised AUTH=PLAIN</tt></a></p>
<dl>
<dd>
This is a bug in the SMTP server.
<p>Some versions of qmail, including that running on
mail.smtp.yahoo.com, have a bug in their implementation of SASL in
their SMTP server, which renders it non-compliant with the
standard.</p>
<p>If the client does not provide an initial response in the command
line for an authentication mechanism whose profile does not have an
initial challenge, qmail issues a bogus response:</p>
<pre>
334 ok, go on
</pre>The problem is the "ok, go on". This violates RFC 4954's requirement
that the text part in a 334 response be a BASE64 encoded string; in other
words, it is a protocol syntax error.
<p>In the case of AUTH=PLAIN, RFC 4422 (page 7) requires that the
encoded string have no data. In other words, the appropropiate
standards-compliant server response is "334" followed by a SPACE and a
CRLF.</p>
<p>The SECURITY PROBLEM came about because the server advertised the
AUTH=PLAIN SASL authentication mechanism outside of a TLS-encrypted
session, in violation of RFC 4616. This message is just a warning, and
is not related the "Authentication cancelled" problem.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="7.48"><strong>7.48 Why do I get the message</strong> <tt>Invalid
base64 string</tt> <strong>when I try to authenticate to a Cyrus
server?</strong></a></p>
<dl>
<dd>
This slightly misleading message is the way that a Cyrus server
indicates that an authentication exchange was cancelled. It is not
indicative of a bug or protocol violation.
<p>The most common reason that this happens is if the Cyrus server
offers Kerberos authentication, c-client is built with Kerberos
support, but your client system is not within the Kerberos realm. In
this case, the client code will try to authenticate via Kerberos, fail
to get the Kerberos credentials, cancel the authentication attempt, and
try the next available authentication technology.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><br></p>
<h2><a name="additional">8. Where to Go For Additional Information</a></h2>
<hr>
<p><a name="8.1"><strong>8.1 Where can I go to ask questions?</strong></a><br>
<a name="8.2"><strong>8.2 I have some ideas for enhancements to IMAP. Where
should I go?</strong></a></p>
<dl>
<dd>
If you have questions about the IMAP protocol, or want to participate
in discussions of future directions of the IMAP protocol, the
appropriate mailing list is imap-protocol@u.washington.edu. You can
subscribe to this list via <a href=
"mailto:imap-protocol-request@u.washington.edu"><tt>imap-protocol-request@u.washington.edu</tt></a>
<p>If you have questions about this software, you can send me email
directly or use the imap-uw@u.washington.edu mailing list. You can
subscribe to this list via <a href=
"mailto:imap-uw-request@u.washington.edu"><tt>imap-uw-request@u.washington.edu</tt></a></p>
<p>If you have general questions about the use of IMAP software
(not specific to the UW IMAP toolkit) use the
imap-use@u.washington.edu mailing list. You can subscribe to
this list via <a href=
"mailto:imap-use-request@u.washington.edu"><tt>imap-use-request@u.washington.edu</tt></a></p>
<p>You must be a subscriber to post to these lists. As an
alternative, you can use the
<strong>comp.mail.imap</strong> newsgroup.</p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="8.3"><strong>8.3 Where can I read more about IMAP and other email
protocols?</strong></a></p>
<dl>
<dd>We recommend <em>Internet Email Protocols: A Developer's Guide</em>,
by Kevin Johnson, published by Addison Wesley, ISBN 0-201-43288-9.</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<hr>
<p><a name="8.4"><strong>8.4 Where can I find out more about setting up and
administering an IMAP server?</strong></a></p>
<dl>
<dd>
We recommend <em>Managing IMAP</em>, by Dianna Mullet &amp; Kevin
Mullet, published by O'Reilly, ISBN 0-596-00012-X.
<p>This book also has an excellent comparison of the UW and Cyrus IMAP
servers.<br></p>
</dd>
</dl>
<p><a href="#top">Back to top</a></p>
<p>Last Updated: 15 November 2007</p>
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