Courier Mail Server

Spec sheet

Product

Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services.Read 4 Oct 2026 · courier-mta.org

Platforms

The source should compile on most Linux and BSD-based POSIX operating systems, and may compile on Solaris and AIX with additional tools.Read 5 Oct 2026 · courier-mta.org

Deployment

It can act as an intermediate mail relay, receive mail for multiple domains, or do both.Read 5 Oct 2026 · courier-mta.org

Integrations

The server can use LDAP, MySQL, or PostgreSQL-based authentication databases and supports LDAP-based mail routing.Read 5 Oct 2026 · courier-mta.org

Security

Courier supports STARTTLS and SSL for ESMTP, IMAP, POP3, and webmail; its ESMTP client can require a certificate signed by a trusted root CA.Read 5 Oct 2026 · courier-mta.org

Support

The site lists an unmoderated courier-users mailing list for questions, bug reports, and comments, plus a separate read-only announcement list.Read 4 Oct 2026 · courier-mta.org

Authentication

Authentication options include PAM, LDAP, MySQL, and PostgreSQL, with PostgreSQL identified as beta on the features page.Read 5 Oct 2026 · courier-mta.org

Calendaring

Its webmail module includes basic web-based calendaring and scheduling, including a personal event calendar.Read 5 Oct 2026 · courier-mta.org

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.Read 5 Oct 2026 · courier-mta.org

Distribution

The download page offers the complete server source tarball and separate packages for components including IMAP, SqWebMail, and maildrop.Read 5 Oct 2026 · courier-mta.org

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.Read 4 Oct 2026 · courier-mta.org

Filtering

Integrated mail filtering supports administrator-installed external filters and recipient-specified rules through maildrop.Read 5 Oct 2026 · courier-mta.org

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.Read 4 Oct 2026 · courier-mta.org

Limits

Courier does not implement ETRN, and its integrated mailbox access components do not support mbox mailboxes.Read 5 Oct 2026 · courier-mta.org

Mail services

Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services.Read 5 Oct 2026 · courier-mta.org

Mail storage

Maildir is its native mail storage format, and integrated IMAP, POP3, and webmail components support maildir-based mailboxes only.Read 5 Oct 2026 · courier-mta.org

Mailing lists

Courier includes a mailing list manager with automatic bounce processing.Read 4 Oct 2026 · courier-mta.org

Relay protection

The site says Courier is a closed mail relay by default and cannot accidentally be configured as a completely open relay.Read 5 Oct 2026 · courier-mta.org

Standalone components

The IMAP server, SqWebMail webmail CGI, and maildrop filter are also offered as separate packages usable with other mail servers.Read 4 Oct 2026 · courier-mta.org

Storage

Maildir is its native storage format; the integrated POP3, IMAP, and webmail servers work with maildir mailboxes only.Read 4 Oct 2026 · courier-mta.org

Transport security

The site lists STARTTLS and SSL support for ESMTP, IMAP, POP3, and webmail, and says the ESMTP client can require trusted-root-signed X.509 certificates.Read 4 Oct 2026 · courier-mta.org

Web administration

Most configuration can be adjusted through a web-based administration module.Read 5 Oct 2026 · courier-mta.org

Plans and prices

Every Courier Mail Server plan and price →

Where Specifiction places it

• Mail Server Software#1 of 348.5