Exim

exim.org · checked 8 Oct 2026

#8 · Email Server Software #12 · Mail Server Software

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How it plugs in

—Public API

NoOpen source

YesFree tier

Signal on Email Server Software6.2#8 of 33

Exim is a mail transfer agent for hosts running Unix or Unix-like operating systems.

Pricing

EximGNU General Public Licence · self-managed mail transfer agentFree

As exim.org lists them, checked 8 Oct 2026.

Near it

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Runs on

Web
Windows
Mac
Linux
iOS
Android

Facts

Website: exim.org
Price: Free tier
Free trial: No
Download verification: Published source tarballs are cryptographically signed with OpenPGP, and signatures are distributed alongside them.
Filtering: Users can use Sieve filters or Exim’s own filter language, which the manual describes as more powerful than Sieve.
Intended use: The manual says Exim is designed for Internet mail transfer and that using it to send bulk unsolicited email conflicts with the project’s aims.
Mail routing: Exim provides flexible facilities for routing mail and checking incoming mail.
Mail transport: The implemented external transport mechanisms are SMTP and LMTP over TCP/IP, including IPv6.
Policy controls: Access control lists can grant or deny access at points in the SMTP dialogue, including after recipient commands and at the end of a message.
Release signing: The project says all releases receive a signed Git tag.
Scanning integrations: When built with the content-scanning extension, Exim can pass messages to external virus or spam scanning software through its ACL mechanism.
Security updates: The website identifies version 4.100.1 as a security release addressing four listed security issues.
Support and community: The project provides announcement, development, and user mailing lists, including searchable archives for the user list.
Virus and spam scanning limit: The manual says Exim’s basic incoming-message scanning is not comprehensive enough for full virus or spam scanning and recommends specialized additional software.
Windows support: Configuration files exist for compiling Exim in the Cygwin environment on Windows, but the manual does not explain running Exim there.

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