Tuesday, 8th August 2006Email Protocols (IMAP, POP3, SMTP, HTTP)

Covering the basics of Email Protocols, this article is meant as a primer for thos wishing to know more about what goes on behind the Send / Recieve button.

In networking, a protocol (from the Greek protocollon, which was a leaf of paper glued to a manuscript volume, describing its contents) is a set of rules that two or more points abide by to communicate a specific type of data. Data for protocols is broken down in to "packets" of data and as well as defining what these packets contain, a protocol defines how an initial communication is established (what sort of 'handshake' or 'introduction' two computers must have before they begin sending data).

There are many email protocols out there but this article only briefly covers the main three:

IMAP Protocol (Internet Message Access Protocol)

The IMAP protocol's primary advantage over other messaging protocols is its ability to leave your messages and inbox structure on the mail server that serves you. As well as providing a level of backup / redundancy, IMAP also allows you to access ALL of your emails (inbox, sent items, deleted items, etc) from multiple computers. As an example, you could go home and recieve and send multiple emails on your home PC then go to work and see the same messages in your email client at work. Due to the fact that an email client (email program) is accessing all of your previous emails, the protocol is designed to work using minimal bandwidth, making it useful for people on slow connections or mobile devices.

While the IMAP protocol is a beautiful thing, it is also a very complex and difficult protocol to work with, meaning many software companies shy away from it. One of the best IMAP clients available at the moment is actually free - Mozilla's Thunderbird (www.mozilla.org) has a fantastic ever-growing feature set allowing a great deal of tweaking. When compared to Mozilla Thunderbird (www.mozilla.org), Microsoft's Outlook 2003 offering really is put to shame as it is so buggy as to be unusable.

POP3 Protocol (Post Office Protocol 3)

The POP protocol is probably the most widespread and commonly used protocol, providing a simple, standardized way for users to download messages to their computers.

When using the POP protocol all your email messages are downloaded from the mail server to your local computer, you have the option to leave copies of your email on the server as well. While leaving messages on the server provides some of the benefits of IMAP (in that you could access them from another computer later), the messages are lumped together with no carrying over of read-status, folder structure, etc.

SMTP Protocol (Simple Mail Transfer Protocol)

Unlike IMAP and POP3, the SMTP protocol is used to send messages to people.

HTTP Protocol (Hyper Text Markup Language)

The HTTP protocol is not actually an email protocol but is here as it is often used to access email from web based email systems such as Hotmail, Outlook Web Acess, Yahoo Email, etc.