Exim is a message transfer agent (MTA) developed at the University of
Cambridge for use on Unix systems connected to the Internet. It is
freely available under the terms of the GNU General Public Licence. In
style it is similar to Smail 3, but its facilities are more general.
There is a great deal of flexibility in the way mail can be routed, and
there are extensive facilities for checking incoming mail. Exim can be
installed in place of sendmail, although the configuration of exim is
quite different to that of sendmail.