Exim serves as a mail transfer agent (MTA) for Unix-like operating systems. Initially developed by Philip Hazel in 1995 for the University of Cambridge Computing Service's email systems, Exim is released under the GPL, allowing users to freely download, utilize, and modify it. While it shares some similarities with Smail 3, Exim has evolved to offer greater user-friendliness and flexibility. Both Exim and Smail 3 operate on the Sendmail design model, where a single main binary manages all MTA functionalities. Although this monolithic architecture is sometimes viewed as less secure and slower, Exim boasts a superior security record compared to Sendmail and matches the performance of Qmail and Postfix, particularly in advanced functions like queue management, address routing, and testing. Notably, Exim lacks a built-in Graphical User Interface (GUI) for configuration, although some Linux distributions may provide one, enhancing its accessibility for users who prefer a visual approach. As a result, Exim remains a versatile choice for those looking to manage email systems effectively.