Courier Mail Server

courier-mta.org · checked 5 Oct 2026

#3 · Mail Server Software

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How it plugs in

—Public API

NoOpen source

YesFree tier

Signal on Mail Server Software6.3#3 of 34

Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services.

Pricing

Courier Mail ServerSource code distributed under the GNU General Public LicenseFree

As courier-mta.org lists them, checked 5 Oct 2026.

Near it

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Runs on

Web
Windows
Mac
Linux
iOS
Android

Facts

Website: courier-mta.org
Price: Free tier
Free trial: No
Authentication: Authentication options include PAM, LDAP, MySQL, and PostgreSQL, with PostgreSQL identified as beta on the features page.
Calendaring: Its webmail module includes basic web-based calendaring and scheduling, including a personal event calendar.
Compatibility: Courier can be installed on systems previously running sendmail or Qmail, but the site says it is not a fully compatible replacement for either.
Deployment: It can act as an intermediate mail relay, receive mail for multiple domains, or do both.
Distribution: The download page offers the complete server source tarball and separate packages for components including IMAP, SqWebMail, and maildrop.
Download: The download page lists Courier 2.0.7, dated 02-Aug-2026, as a source code tarball containing the mail server, IMAP server, webmail server, and maildrop filter.
Filtering: Integrated mail filtering supports administrator-installed external filters and recipient-specified rules through maildrop.
Integrations: The server can use LDAP, MySQL, or PostgreSQL-based authentication databases and supports LDAP-based mail routing.
Limitations: Courier does not implement ETRN and is not a fully compatible replacement for sendmail or Qmail; its integrated mailbox servers do not support mbox.
Limits: Courier does not implement ETRN, and its integrated mailbox access components do not support mbox mailboxes.
Mailing lists: Courier includes a mailing list manager with automatic bounce processing.
Mail services: Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services.

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