Courier-IMAP is a fast, scalable, enterprise IMAP server that uses Maildirs. Many E-mail service providers use Courier-IMAP to easy handle hundreds of thousands of mail accounts.
With the built-in IMAP and POP3 aggregation proxy in Courier-IMAP 4.0, the only practical limit to Courier's horizontal scalability is available LAN bandwidth. In proxy mode, a pool of Courier servers receive IMAP and POP3 connections from clients, wait for the clients to send a login request, look up the mail account's server, and establish a proxy connection to the actual server that hosts the mail account.
Please note that this IMAP server does NOT handle traditional mailbox files (/var/spool/mail, and derivatives), it was written and optimized for the specific purpose of providing IMAP access to Maildirs.
"Maildir" is a directory-based mail storage format originally introduced in the Qmail mail server, and adopted as an alternative mail storage format by both Exim and Postfix. Courier-IMAP is popular on Qmail/Exim/Postfix sites that are configured to use maildirs. The primary advantage of maildirs is that multiple applications can access the same Maildir simultaneously without requiring any kind of locking whatsoever. Maildir is a faster and more efficient way to store mail. It works particularly well over NFS, which has a long history of locking-related woes.
This is the same IMAP server that's included in the Courier mail server, but configured as a standalone IMAP server that can be used with other mail servers - such as Qmail, Exim, or Postfix - that deliver to maildirs. A Courier/Postfix combination is very popular. If you already have Courier installed, you do not need to download this version. If you install this version, you must remove it if you later install the entire Courier server. It's possible to have both versions installed, but this will require a delicate juggling act that you'll have to learn on your own.
What's New in This Release: [ read full changelog ]
· Makefile.am (imapd.cnf): Compatibility fixes.
· maildir/maildirwatch.c (maildirwatch_alloc): Use alarm() to kill the process if FAMOpen() takes more than 15 seconds to return. Should prevent a hung process if FAM/Gamin is fubared.
· pop3dserver.c: Make printed() and putchar() macros.
· imapd.cnf pop3d.cnf (default_md): added default_md = sha1
· rfc822/rfc822.c (rfc822_print_common_nameaddr): Prevent segfault if address decode fails.
· Fix make check failure when libidn is not available.
· Rebuilt man pages with updated stylesheets.