Exim is an Open Source Mail Transfer Agent (MTA) which deals with routing, receiving and delivering of Electronic Mail. Exim service serves to be a great replacement of “Sendmail” service which comes bundled with most of the distro. The first version of Exim was written in 1995 by Philip Hazel for use in the University of Cambridge Computing Service’s e-mail systems. The name initially stood for experimental Internet Mailer. It was originally based on an older MTA, Smail-3, but it has since diverged from Smail-3 in its design and philosophy.