Courier-IMAP 4.1.2

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 Couriers 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 accounts 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 thats 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. Its possible to have both versions installed, but this will require a delicate juggling act that youll have to learn on your own.
Enhancements:
- A bug in quota calculation on 64-bit platforms has been fixed.
- The IMAP server will try to log the clients bandwidth usage if the server process gets killed by a signal.
- New messages created by the IMAP server will use the servers umask setting.
- Many compiler warnings, error messages, and manual page typos were fixed.