Friday, June 1, 2012

Email Protocols

When sending or receiving emails, email client needs certain protocol to talk to email servers. In general, there are five protocols for incoming and outgoing emails, namely IMAP, POP3, SMTP, MAPI and HTTP.

IMAP (Internet Message Access Protocol), latest version is 4, so also called IMAP4. It is a client/server protocol in which e-mail is received and held for you by your Internet server. It is two way, so changes on client will reflect on server as they are connected (online).

POP (Post Office Protocol), latest version is 3, so also called POP3. It provides a simple, standardized way for users to access mailboxes and download messages to their computers, then act on the downloaded messages without needing to stay connected (online). It is always one way, from server to client.

SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your email to the recipient's mail server. The SMTP protocol can only be used to send outgoing emails, not to receive incoming emails.

MAPI (Messaging Application Programming Interface) is Microsoft's proprietary email protocol.  It provides greater functionality than IMAP for Outlook email clients interacting with an Exchange email server. It only works on this combination, not others.

HTTP (Hypertext Transfer Protocol) is the application protocol for web communication, but it can be used for accessing mailbox, a.k.a. web based email. For instance, Exchange server can be accessed by Outlook Web Access (OWA), Hotmail/Gamil etc can be accessed using browsers.

No comments:

Post a Comment