Mailismus is a secure high-performance mail server that runs on any Unix/Linux, Windows or MacOS X platform. It just requires Java (Java 7 or later).
Full-featured evaluation licences are available free of charge - see Ordering link on left menu.

Features include:

See the Admin Guide for the full details.
Mailismus is powered by the Network Application Framework (NAF).

View MTA Queue View SMTP Grey-List
MTA-Queue screenshot GreyList screenshot

Some typical deployment scenarios to which Mailismus is suited are:

In addition to its performance and anti-spam measures, Mailismus is also distinguished by the depth and breadth of its logging options, providing for formal audit logs and exhaustive SMTP, IMAP and POP3 transcripts, in addition to the standard trace-level application logging you would normally expect.
Never again need you face the frustration of submitting messages into a black hole and wondering what happened to them and why.