Postfix is an MTA (Mail Transfer Agent) for sending and receiving emails. It was developed due to the short coming found in Sendmail. The difference between the Postfix and Sendmail is that Postfix is very easy to install and configure, while sendmail on the other hand is a bit hard to work with and difficult to troubleshoot. The reason behind this is that sendmail is a single process or single binary which combines all its functions and modules built in it, so this single daemon should always be running. Postfix comes with different independent modules, responsible for delivery routing messaging and filtering etc. these modules are separate entity independent of postfix such as SMTP client, SMTP Daemon, and applications like cleanup, trivial re-write, queue manager (qmgr), pipe, local, pickup and maildrop, all interacting with each other to make a fully fledged email server.

Post has support for Regular expression such as Perl regular expression which we’ll talk about it later in this article.

Postfix Block Diagram

The image below show the email delivery process both local and remote messages.

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