Pop3 and SMTP Pop3 POP3 (Post Office Protocol 3) is the most recent version of a standard client/server protocol for receiving e-mail in which e-mail is received and held for you by your Internet server. You (or your client e-mail receiver) check your mail-box on the server and download any mail. POP can be thought of as a 'store-and-forward' service. IMAP IMAP (Internet Message Access Protocol) is an alternative protocol where your e-mail is viwed at the server as though it was on your client computer. E-mail can be kept on and searched at the server and e-mail messages deleted locally are still on the server. IMAP can be thought of as a remote file server. SMTP SMTP (Simple Mail Transfer Protocol) deals with the transfer of e-mail across the Internet. E-Mail E-mail is sent with SMTP and a mail handler receives it on the recipient's behalf. The e-mail is then read using POP or IMAP.