Projects / Courier-IMAP


Courier-IMAP is a lightweight server that provides IMAP access to maildir mailboxes. It supports folders, custom authentication modules, and virtual mailboxes. A compatible POP3 server is also provided. The source code is based on the IMAP module in the Courier Mail Server, but this build is independently repackaged to work with any other MTA that delivers to maildir format mailboxes.

Operating Systems

Recent releases

  •  11 May 2009 03:10

    Release Notes: This release has additional logging, adds support for chained SSL certs when using the GnuTLS library, includes minor performance improvements in header parsing, and fixes incorrect matching of empty MIME entities for any SEARCH request.

    •  13 Jul 2008 23:38

      Release Notes: IMAP keyword performance was optimized. Support for SSL certificate-based authentication was added.

      •  25 Nov 2007 16:19

        Release Notes: This release adds the ability to use GnuTLS as an alternative to OpenSSL for SSL/TLS support.

        •  30 Sep 2007 07:06

          Release Notes: This release adds optimizations that can bring significant performance improvements on NFS with some usage patterns. Additionally, the server attempts to detect and report server clock skew when using NFS. The license has been updated to GPL 3.

          •  30 Dec 2006 20:37

            Release Notes: A bug in quota calculation on 64-bit platforms has been fixed. The IMAP server will try to log the client's bandwidth usage if the server process gets killed by a signal. New messages created by the IMAP server will use the server's umask setting. Many compiler warnings, error messages, and manual page typos were fixed.

            Recent comments

            27 Jun 2007 11:03 danabrunson

            Re: Anyone done IMAP over ssl with Courier?

            I run non-SSL on

            > "localhost"

            > only, and SSL on the real IP address. I

            > had to

            > make one change to

            > /usr/lib/courier-imap/etc/imapd-ssl.config.

            > I

            > commented out the line that includes

            > imapd-ssl.config. Otherwise, the

            > settings for the

            > secure server get used by the insecure

            > one.


            > I subscribed to the mailing list and

            > submitted

            > this change, but I got back a nasty

            > message saying

            > that they wouldn't accept my email

            > because they

            > claimed I was NOT subscribed.


            > Eric



            Could you elaborate on how you set it up to accept non-ssl on localhost only?



            03 Jan 2005 11:31 zerbey

            The best Maildir IMAP server
            It just keeps getting better with every release, straightforward to set up and then you just let it run and forget about it. All servers should be this good.

            Version 4 offers a significant speed boost over version 3 as well.

            21 Apr 2003 13:53 Gridlocke2003

            Netscape Fixed needed for POP3.

            Should add a compile option at build for this problem with Netscape. Netscape clients (4.7 and such) using POP3 for login, STRIP "" to just "username" (Netscape strips off everything after the @ symbol). This breaks compatiblty with ISP's that have users setup using the full e-mail address for POP3, like in Outlook Express.

            This can be annoying if you have a virtual database with courier and the login names are "". The solution has been to make the users in Netscape use "%" or ":", like "", or "" with a replace routine for the login to change "%", and/or ":" to "@", or adding "" to the database to fix this problem.

            07 Dec 2001 06:13 Remo

            billenium-bug patch
            Is there any patch for the billenium-bug for courier ? My Netscape Communicator 4.79 don`t display subject correctly. I renamed my old messages delivered to Maildir vith Qmail but i don`t see any change. Can my someone help ?

            Other info about millenium-bug: <>

            08 Jun 2001 12:03 Bastus

            new mail notification

            Does anyone of you know how to set up an imidietly mail notification to an IMAP client (in read in the RFC that the server has to send an "EXIST" to the client when the mailbox size changes - new mail is delivered)? I know that this normally is a a feature of IMAP servers but can't get it working with Courier-IMAP. In case of this isn't supported by Courier-IMAP do you know how to set it up with UW-IMAP and Maildir (I cou'dl get this either).

            Thanks in advance

            CU Bastus


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