The most popular message transfer agent (MTA) in Linux

MTA (Mail transfer Agent)

-For server administrators, the message transfer agent is the most important tool. The main task of the MTA is to send e-mail messages from one host to another host. The MTA uses SMTP (Simple Mail Transfer Protocol) to deliver e-mail messages. To make it clearer to you, the clients we use to send and receive mail are also using SMTP, but they are not MTA. They are just an application that provides some kind of interface for users to send and receive mail. They are called MUA (mial user agent)-Mail user agent.

There are many kinds of mail transport agents in the Linux operating system, each with its own strengths and weaknesses. Some are easy to install and configure, and some have strong security. The most popular MTA in Linux has the following:

Postfix

Sendmail

Qmail

Exim

     

Postfix: Postfix is popular because of its performance and security. It supports mail filtering, called Milter. Milter's function is to allow messages to be scanned by antivirus and anti-spam software before being sent to Postfix. With the standard configuration, Postfix is able to run under less system resources. Like other MTA, Postfix has a primary configuration file. Each configuration of the postfix is table-driven and can be converted to any relational database or text file. It also uses a Perl-compatible regular expression library. Installing postfix is relatively complex compared to other MTA. It supports virtual mailboxes and virtual domains.

Sendmail: in Linux servers, Sendmail is also a very popular and top-level MTA. SendMail is one of the oldest MTA, and its security is slightly worse than that of the other MTA. The main problem with SendMail is that its configuration files are too complex to configure. Now the sendmail is very mature and safe, although its source code is not completely rewritten, may expose other security issues. SendMail support for virtual domains is not as good as the other MTA. SendMail is thought to be able to handle all email related transactions, it also supports Milter, and can invoke external programs to intercept e-mails and other complex things.

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Qmail:Qmail is safe and easy to use than other MTA. It has some built-in modules, such as: POP3, etc. It supports both host and user spoofing, as well as virtual domains. Its configuration files are simple and easy to manage. Of course, QMail also has some drawbacks: some manual operations are required when installing qmail, and fewer documents than other MTA. Since 1998, QMail has stopped the release of new releases, but its patch packs are still being released. By the way, QMail is known as the most patched MTA in history. QMail invented the Maildir format, which can store and deliver e-mails very quickly, reliably, and securely. QMail only uses very small CPU cycles and is suitable for processing large amounts of e-mail.

Exim: The biggest feature of Exim is that users can customize the rules. For example, we can create rules to send messages to specific folders. EXIM3 has a lot of security holes, but Exim4 is much safer. It supports host-to-user spoofing, virtual domains, and SMTP relay control for each host. It also supports anti-virus and anti-spam features, and has its own filtering language. Exim also has some weaknesses that, under heavy loads, have a much worse performance than other MTA. Similar to SendMail, Exim uses a single but extremely complex configuration file.

All of the above MTA are the top-level MTA in a Linux environment. If you are a novice, you should start using it from QMail. If you are experienced, then you should know what is best for you.

The most popular message transfer agent (MTA) in Linux