IMAP

IMAP servers

There are basically three main IMAP server solutions:

UW IMAP

IMAP server developped by the University of Washington. Uses a proprietory mailbox format mbx, which is more or less a binary version of the usual mailbox format. A binary package exists on cygwin, but it regularly suffers from locking problems. A patch exists to use maildir format though, but patch seems outdated.

[Courier|Courier IMAP]

Courier-IMAP is a fast, scalable, enterprise IMAP server that uses Maildirs.

Cyrus IMAP

Developped by Carnegie Mellon. Also uses a private mailbox format.

Dovecot IMAP

A very fast IMAP server focusing on security, which supports mbox and Maildir.

Courier IMAP

References

• Courier IMAP homepage
  • maildir - E-mail directory
  • Courier FAQ
• On openSUSE:
  • Package doc at /usr/share/doc/packages/courier-authlib and /usr/share/doc/packages/courier-imap.
• On Ubuntu:
  • https://help.ubuntu.com/community/Courier
• Manpages & package documentation:
  • maildirmake(1)
  • couriertcpd(1)
  • imapd(8)
  • userdb(8)
  • makeuserdb(8)
  • /usr/share/doc/courier-doc (on Ubuntu, with package courier-doc installed)

Courier IMAP on Ubuntu

To install Courier IMAP:

• Install the required packages:

sudo apt-get install courier-imap courier-doc courier-imap-ssl

• Create /etc/courier/userdb.dat

sudo su
pw2userdb >/etc/courier/userdb
chmod 600 /etc/courier/userdb
makeuserdb
maildirmake /etc/skel/Maildir            # Create Maildir directory for all new users

To use the password from /etc/courier/userdb (and not from PAM) (as root):

• Edit the file /etc/courier/authdaemonrc, and change it as follows:

authmodulelist="authuserdb"

• Restart the daemon:

/etc/init.d/courier-authdaemon restart

• Change the password for user username and commit the changes

userdbpw -md5 | userdb username set systempw
makeuserdb

• Test the new password with

nc imapserver 143
01 LOGIN username password
02 LOGOUT

Courier IMAP on openSUSE

Binary package for Courier IMAP is available on openSUSE (package courier-authlib and courier-imap). However it conflicts with the default IMAP server, (UW IMAP), which must first be uninstalled.

Courier IMAP on Cygwin

See the page dedicated to Courier Cygwin.

Synchronizing IMAP

offlineimap

offlineimap allows you to read the same mailbox from multiple computers and ensures that your changes will be automatically reflected on all computers.
See Yoni's page at [1].

imapsync

imapsync is very easy to use to migrate from one mailbox to another. The procedure here is based on the one given here [2]

# Migrating from me@host1.com to me@host2.com
echo 'password' > pwd1    # We hide the password in files so that they don't appear with the command "ps aux"
echo 'password' > pwd2
chmod 600 pwd1             
chmod 600 pwd2
imapsync --host1 host1.com --user1 me@host1.com --passfile1 pwd2 --host2 host2.com --user2 me@host2.com --passfile2 pwd2
rm -f pwd1
rm -f pwd2

However it seems that imapsync is one-way only, and so not suitable for syncing live the same mailbox between several computers [3].
For this purpose, better use offlineimap.

Testing IMAP

Tools

Simply use tool like telnet to connect to the IMAP server. Or equivalently use netcat or socat:

% telnet server 143
% nc server 143
% socat - TCP:server:143

!!! Problem when connecting to Microsoft servers !!! - These servers explicitly require CRLF as line-terminator, not CR as sent by Linux tools. Only workaround so far is to connect through a windows telnet.

Scripts

Here some scripts to test that an IMAP server is working properly.

• To quickly test an imap server using telnet use:

% telnet server 143
01 LOGIN username password
02 LIST "" *                 # show all available mailboxes
03 SELECT mailbox            # mailbox: e.g. INBOX
04 LOGOUT

• To show the information about a mailbox:

% telnet server 143
04 STATUS mailbox (MESSAGES)

Between () you can place one or more of the following: MESSAGES, UNSEEN, RECENT UIDNEXT UIDVALIDITY

• And one of the following commands to view a message (1 is the first message * is wildcard for all):

05 FETCH 1 ALL               # All IMAP headers
05 FETCH 1 FULL              # Full headers and body info
05 FETCH 1 BODY              # Body
05 FETCH 1 ENVELOPE          # Envelope
05 FETCH * FULL              # All email

• To fully retrieve a message use:

06 UID fetch 1:1 (UID RFC822.SIZE FLAGS BODY.PEEK[])

Troubleshooting

• Can't connect
  • Frequent mistake is that ~/Maildir was not created. Create the Maildir directory with:

su accountname
maildirmake ~/Maildir