POP3 (Post Office Protocol 3) is a form of obtaining email that gets all email from the mail server and copies it to your computer and then deletes it off of the mail server. This is useful for many reasons. It is faster then IMAP since it does not have to retrieve information every time an email is requested. It saves space on the mail server since after a POP3 operation is performed all mail that was obtained by the client is deleted from the server. And it allows you to view your email when you are not online making it ideal for anyone who is using a dial up connection. However if you often check your email from multiple locations POP3 may not be the best choice since it removes mail from the server, meaning that if you check your email in outlook from one computer with POP3 and a then attempt to check it from another computer you will not receive any email since the email is no longer on the server.

IMAP (Internet Message Access Protocol 4). Is a form of obtaining email that simply shows you the email that is on the server rather then copying the message to your computer. IMAP is nice since it will not automatically download any email that could be harmful, and it makes checking your email from multiple computers fast and easy. IMAP is very popular with roaming customers who check their email from many different computers. IMAP can often be slower then POP3 since it has to query the server every time you want to view an email and it has to retrieve header information every time you check your mail (which means checking mail will take longer as well). The current version of the IMAP protocol is IMAP4.