Exim is a mail-transfer agent (MTA), which can be used in Unixllike operating system. Philip Hazel wrote the first version in 1995 for the University of Cambridge Computing Service's email systems. Exim is available under the GPL and is free to download and modify. Exim is somewhat similar to Smail 3. However, it has diverged from it and now exceeds it in ease-of-use and flexibility. Both follow the Sendmail design model, where one main binary controls all facilities of the MTA. Some consider this monolithic design to be less secure and slower. However, Exim's security record and speed are better than Sendmail. It excels in advanced areas like address routing, queue handling, and testing. Exim does not have a Graphical User Interface (GUI), but some Linux distributions do.