A protocol used to retrieve e-mail from a mail server. Most e-mail applications (sometimes called an e-mail client) use the POP protocol, although some can use the newer IMAP (Internet Message Access Protocol) or APOP. POP stands for "post office protocol" not your dear old dad. A "pop" account is any real e-mail account which uses a password and username to retrieve mail from a virtual server. The username would be yourname@yourdomain.com and the password would usually be a mixture of letters and numbers.