Exim is a free, open-source MTA produced at Cambridge University, and it is popular with users of Linux and other UNIX-like operating systems thanks to its customizability and helpful community.
Exim’s Advantages
At the moment, Exim is the standard mail transfer agents for Debian-based Linux systems such is Ubuntu, probably because it can be easily customized and configured.
Variables in Exim
The ability to declare variables is numbered among its handier features. Variable values can be taken from incoming emails and subsequently used for things like message filtering.
Exim also has a native scripting language that allows users to create bespoke scripts for processing emails.
Logs
Users appreciate Exim for its logging capabilities, which exist in triplicate to fight spam. These logs are called ‘main’, ‘panic’, and ‘reject’.
Troubleshooting
Solving problems is made somewhat easier by Exim’s well-established and very active online community. Bug hunting users will also benefit from the plethora of online documentation that exists.
Customization
Exim is very customizable and is compatible with Sendmail. It has proved its worth as an MTA. The Exim Configuration Manager interface within the Service Manager in WHM is where users go to customize it, or they can make changes to the exim.conf file.
Disadvantages
Complexity
All that flexibility comes at a price that some users are unwilling to pay, i.e., it’s complicated, which could be seen as a disadvantage. That supportive community is one symptom of this complex beast. If you want to maintain it successfully then you’re probably going to need help.
Queue Processing Performance
Many high-volume web applications rely on Exim because it can efficiently manage vast rivers of incoming emails, but these can back up and hinder the server’s ability to process the queue.
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