An email server is a system or set of systems which handles the receiving and sending of email messages on the Internet. There are multiple types of email servers such as SMTP servers which use the Simple Mail Transfer Protocol that is used for e-mail transmission. An SMTP server usually runs in conjunction with an IMAP or POP3 server whose purpose is to provide e-mail retrieval and/or storage. Running an email server is not an easy task. It requires installing, configuring, understanding and maintaining a number of different services. Postfix is a free open source mail transfer agent (MTA). It is easy to administer, fast and as well as the secure MTA. It’s an alternative to Sendmail, which is the default MTA for RHEL. As you can imagine, there are number of different SMTP, POP3 and IMAP servers out there. In this article, we are talking Postfix, Dovecot and DKIM so we will walk you through the steps of installing and configuring an email server with Postfix...