POP stands for Post Office Protocol. POP is a standard client/server protocol for sending and receiving email.

The emails are received and held on the email server until you pick it up with a client email program on your PC or mobile phone, like Outlook, Outlook Express, Entourage, Mac Mail, Thunderbird etc.

IMAP stands for Internet Message Access Protocol. IMAP is another standard protocol for sending and receiving email.

The emails are received and held on the email server and can be downloaded via an email client program on your PC or mobile phone or both, like Outlook, Outlook Express, Entourage, Mac Mail, Thunderbird etc.

IMAP represents an improvement over POP because email stored on an IMAP server can be manipulated from several computers (a computer at home, a workstation at the office, etc.) without having to transfer messages back and forth between computers. POP was designed to support email access on a single computer.