Courier-IMAP
   Commercial software that works with Courier-IMAP (next)

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   Copyright 1999-2008, 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 its built-in IMAP and POP3
   aggregation proxy, Courier-IMAP has practically infinite horizontal
   scalability. In a proxy configuration, a pool of Courier servers service
   initial IMAP and POP3 connections from clients. They wait to receive the
   client's log in request, look up the server that actually holds this mail
   account's mailbox, and establish a proxy connection to the server, all in
   a single, seamless process. Mail accounts can be moved between different
   servers, to achieve optimum resource usage.

   The only practical limitation on Courier-IMAP is available network and I/O
   bandwidth. If you are new to Courier-IMAP, this may sound a bit
   intimidating. But you do not need to tackle everything at once. Start by
   taking small, easy steps. Your first step will be to set up a small
   Courier-IMAP server, using it like any other traditional IMAP service, on
   a single server. After you gain experience and become comfortable with
   Courier, you can then begin exploring its advanced features.

   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.
   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.