Understanding POP3 and IMAP

Chances are you've used email once or twice in your life. Until now, your primary method of retrieving mail might have been a web client. That's a perfectly acceptable, if not thoroughly boring, solution. Might we then suggest the raw power of the Mail client. It lives on your desktop or smartphone and it will make you a man. Pure and simple.

However, one does not simply walk into Mordor, in this case. Mail clients demand information about where your mail is coming from and these general come in two flavors: POP3 and IMAP.

Both are email protocols. Both accomplish the same end result. Yet, each has its own unique way of handling your mail.

POP3
Also known as Post Office Protocol ver. 3 is a popular email retrieval system that pulls stored messages from a remote server over the Internet. Specifically, and here is where it differentiates from IMAP, POP3 works on the basis of download and delete. Meaning, with a POP mail account, your client contacts the server, downloads the message to your local machine, and finally your server deletes that message.

The con in this protocol, is that messages that are downloaded cannot be redownloaded from the server. Meaning if your local storage is deleted, so are your messages. There are of course some exceptions to the rules as some POP3 servers will allow you to keep messages on the server for a set amount of time.

Learn more about POP3 here: http://en.wikipedia.org/wiki/Post_Office_Protocol

IMAP
Also known as Internet Messages Access Protocol, IMAP is the other popular email retrieval system. Unlike POP3, IMAP allows a mail client to access a remote mail server. By default, mail is not stored locally, rather a gateway is created to the message. You view, reply, forward, etc. via your mail client.

Many mail clients offer an offline mode for IMAP, where mail is downloaded from the server to a local machine, however, the mail is not removed from the remote server. Rather, it waits for the user to dictate its use. This also means multiple machines can access the same IMAP account and each display the same messages. If a user chooses to delete a message on one machine, the server takes this into effect and syncs this choices across the other mailboxes.

The downside to IMAP is online storage. Providers offer a set amount of space and since the messages aren't downloaded, this may cause an inbox to fill up and bounce back incoming messages. This is a very rare concern, since most providers allow for large amounts of inbox space.
Learn more about IMAP here: http://en.wikipedia.org/wiki/IMAP

Finally, Andy mentioned using Gmail as a middleman for all your various mail accounts. It's actually quite simple to do and effective considering Gmail's spam filters. Find out more here: http://mail.google.com/support/bin/answer.py?answer=22370