Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems or Unix-like operating systems connected to the Internet. 

It was designed on the assumption that it would be run on hosts that are permanently connected to the Internet. However, it can be used on intermittently connected hosts with suitable configuration adjustments.

It is freely available under the terms of the GNU General Public Licence. There is a great deal of flexibility in the way mail can be routed, and there are extensive facilities for checking incoming mail.

Blueloop utilise Exim extensively as a front end email router and email management agent integrating it with virus and spam checking tools such as Clam AV and Spam Assassin to provide a comprehensive email front-end solution for our customers. The Exim system is suitable for all size of organisation and delivers a highly flexible solution.