Web based virtual user administration interface for Postfix mail
Universal server
Anti Spam SMTP Gateway
The first Open-Source high-performance MTA for high-volume senders
Fast and easy-to-use webmail front-end for your existing mail server.
Zentyal is a Linux Small Business Server
Linux for for small offices and medium enterprises
Web and API based SMTP testing
Full SMTP/Mail server Appliance in 5 minutes
Easy installation and configuration of a complete mail server
File system benchmark
Open Source Anti-Spam and Anti-Virus Gateway
To synch and encrypt all sorts of data across different sources
Ciphermail email encryption gateway (S/MIME, OpenPGP, PDF encryption)
javascript to convert thunderbird/seamonkey filters to sieve rules
Webkosa is the open source edition of Webcrossing.
File scanning spam filter MDaemon plugin.