           [1]Courier-IMAP - logo by Bas Boudrie <bboudrie@hetnet.nl>

                                                           For the last       
                                                           several years      
                                                           Courier-IMAP's     
                                                           home page has been 
                                                           hosted by          
                                                           [2]inter7.com.     
                                                           Their support is   
                                                           greatly            
                                                           appreciated.       

   Copyright 1999-2004, Double Precision, Inc. This software is distributed
   under the terms of the GNU General Public License. See COPYING for
   additional information.

   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 servers running Courier receive IMAP and POP3 connections
   from clients, wait for the client's 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 [3]directory-based mail storage format originally
   introduced in the Qmail mail server, and adopted as an alternative mail
   storage format by both [4]Exim and [5]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.
   [6]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 [7]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 has some popularity. 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.

   Courier-IMAP implements several extensions to the basic Maildir mail
   storage format in order to support some additional features, such as
   folders and "soft" quotas. This is done in a way that's backwards
   compatible with the standard Maildir users (although, of course, they will
   ignore the additional features). Other software that understands and uses
   the same Maildir extensions is [8]SqWebMail, and [9]maildrop.

References

   Visible links
   1. http://www.courier-mta.org/imap/
   2. http://www.inter7.com/
   3. http://www.qmail.org/man/man5/maildir.html
   4. http://www.exim.org/
   5. http://www.postfix.org/
   6. http://www.courier-mta.org/mbox-vs-maildir/
   7. http://www.courier-mta.org/
   8. http://www.courier-mta.org/sqwebmail/
   9. http://www.courier-mta.org/maildrop/
