Chapter 5. SMTP and Postfix
The Simple Mail Transfer Protocol (SMTP) has been used since 1982 to deliver e-mail messages and attachments to many different types of computer systems. Its ease of implementation and platform independence has made it the standard protocol used to transfer messages between computer systems on the Internet. To understand how e-mail works, you should get to know SMTP.
The Local Mail Transfer Protocol (LMTP) is a newer protocol that can streamline mail transfers without using message queues.
Postfix is one of a few MTAs that support communicating with Mail Delivery Agents (MDAs) using LMTP. This lets Postfix delegate the chore of delivering local messages to one or more MDA programs, thus freeing it up for other duties. ...