Editing Simple Mail Transfer Protocol (section)

===SMTP vs mail retrieval===
SMTP is a delivery protocol only. In normal use, mail is "pushed" to a destination mail server (or next-hop mail server) as it arrives. Mail is routed based on the destination server, not the individual user(s) to which it is addressed. Other protocols, such as the [[Post Office Protocol]] (POP) and the [[Internet Message Access Protocol]] (IMAP) are specifically designed for use by individual users retrieving messages and managing [[email mailbox|mailboxes]]. To permit an intermittently-connected mail server to ''pull'' messages from a remote server on demand, SMTP has a feature to initiate mail queue processing on a remote server (see [[#Remote Message Queue Starting|Remote Message Queue Starting]] below). POP and IMAP are unsuitable protocols for relaying mail by intermittently-connected machines; they are designed to operate after final delivery, when information critical to the correct operation of mail relay (the "mail envelope") has been removed.