Dovecot and Exim are mail transfer agents (MTAs) commonly found in Linux servers. They provide services such as email storage, delivery, and retrieval for users. If you're configuring a new server or updating its software, it's helpful to know the differences between the two packages to choose the right solutions for your environment. Both MTAs have similar functions and serve different purposes in an email server; one is not necessarily better than the other. But their usage scenarios are very different. Let's explore some of these differences in detail in this article.
Exim:
-> Exim is one of the most widely used email server software for Unix-like operating systems such as Linux and Solaris. It was developed as free software at the University of Cambridge under the terms of the GNU General Public License. It is an open-source MTA. Users can use it, study the code, and modify it.
-> Exim is one of the open-source mail servers and, therefore, one of the best mail transfer agents in terms of customization and configuration possibilities. It is currently used as the default MTA on Debian-based Linux systems, including Ubuntu.
-> The configuration file offers a variety of built-in options, including hooks that enable file and database searches and easy integration with SpamAssassin, ClamAV, and other spam and virus scanners. Some options control what features are exposed, while others allow Exim to handle all sorts of bugs. It also provides hooks for Perl and C programs that can be used to provide custom functionality if you choose the appropriate build options.
-> Exim processes emails in three stages. They are acceptance, forwarding, and delivery. Acceptance is controlled by access control lists (ACLs). ACLs determine who you accept email from, who receives email, and any other conditions you want to impose. Routing is controlled by routers. A router determines where Exim delivers email. Typically this will be either another mail server or a local mailbox.
-> Delivery is controlled by transport. These determine the actual delivery mechanism. Mail can be forwarded to another mail server, written to a mailbox, or forwarded to a command for processing.
Dovecot:
-> Dovecot is an open-source POP3 and IMAP server for Linux operating systems, written primarily with security in mind. Timo Sirainen created the Dovecot and first published it in July 2002. The Dovecot developers primarily aim to create an open-source email server that is lightweight, fast, and easy to set up.
-> Dovecot's primary purpose is to act as a server for email storage. Email is delivered to a server using a Mail Delivery Agent (MDA) and kept for later on the server by using an email client (Mail User Agent or his MUA).
-> It can also act as a mail proxy server, forward connections to another mail server, or as a lightweight MUA to retrieve and manipulate mail on remote servers.
-> Dovecot works with standard mbox, maildir, and its high-performance native dbox format. In addition, it is fully compatible with Courier IMAP and UW IMAP server implementations, as well as email clients such as Outlook or thunderbird that access mailboxes directly.
-> It supports various authentication schemes for Message Submission Agent (MSA) access, POP, and IMAP, including CRAM-MD5 and secure DIGEST-MD5.
-> It is a robust, secure, and fully standards-compliant IMAP/POP3 server. It's also much easier to configure than other IMAP servers and has different authentication mechanisms. It also supports SSL and TLS encryption.
