Last Update 2023-01-22
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MeTA1 is available! (2014-05-25)


MeTA1 is a message transfer agent that has been designed with these main topics in minds:

MeTA1 consists of five main modules of which only one runs as root:

All of these modules run persistently. smtps and smtpc make use of the statethreads library which provides a threading API well suited for Internet applications, smar and qmgr use the POSIX threads API.

The syntax of the MeTA1 configuration file is very simple and resembles C programs or the BIND 9 configuration files. A configuration file does not require any special layout, e.g., tabs or one option per line, but relies on braces and semicolons as structuring elements.

The first release of MeTA1 is intended to be used as a secure and efficient mail gateway. It offers features that are not available in sendmail 8 (or some other open source MTAs), however, it does not provide any builtin support for mail content modification, e.g., masquerading of addresses or changing (addition, removal) of headers. Those features are currently only available via the pmilter API.

Moreover, this version of MeTA1 does not come with a local delivery agent nor with a mail submission program. The documentation explains which programs can be used to perform these tasks and how other features that are not directly available can be implemented.

Policy Mail Filter Support

MeTA1 comes with a policy mail filter library (libpmilter) which offers similar features as libmilter known from sendmail 8. Two milter programs have been ported to the pmilter API and are available in the contrib directory.

Multiple Policy Mail Filters

(2009-01-06) The libpmilter library only provides hooks for a single pmilter, to interact with multiple milters a PMilter Multiplexor is needed. This has been implemented by Sergey Poznyakoff in his mailfromd software.


All aspects of MeTA1 (including installation, configuration, and operation) are documented in a single README file which is available in various formats (dvi, HTML, PostScript, PDF, and plain text) such that the user can select the most appropriate format for her needs. Additionally, a design document is separately available for background reading which also covers the implementation and many other aspects.

MeTA1 License

MeTA1 has basically the same license as sendmail 8. However, it contains several other modules (e.g., Berkeley DB, statethreads) which come with their own licenses.

MeTA1 Source Code

MeTA1 source code is available for download. It comes with a README file in various formats.

Latest Release

The latest version of MeTA1 is 1.1.Alpha19.0 (2022-09-25)
Note: there is an important patch for it (2023-01-22)

MeTA1 Projects

There are many possible projects that would help MeTA1 gain more traction as they provide features that have (repeatedly) been asked for.

MeTA1 History

MeTA1 is a fork of the sendmail X project.

Comparison with other MTAs

What are the differences between various modern MTAs?

CA for https

The CA cert for the web site and the e-mail server can be used for authentication.

MeTA1 Feedback

Please send feedback about MeTA1 to

< MeTA1 + feedback (at) MeTA1 . org >
(sorry for the obfuscation, replace (at) with @ and remove the spaces)
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