What is a POP Mail Server?

A Post Office Protocol (POP) mail server is a server that complies with the RFC standard 1939.

Here is a basic run down.

The Post Office Protocol - Version 3 (POP3) is intended to permit a workstation to dynamically access a maildrop on a server host in a useful fashion. Usually, this means that the POP3 protocol is used to allow a workstation to retrieve mail that the server is holding for it.

POP3 is not intended to provide extensive manipulation operations of mail on the server; normally, mail is downloaded and then deleted. A more advanced (and complex) protocol, IMAP4, is discussed in [RFC1730].

In Plain English:

A POP mail server (or simply "POP server") is the most common form of incoming email server. Basically, the POP server is what receives the email and is almost always used with an SMTP server, which is the outgoing server. The best way to find out the address of your POP server is to ask the company who is providing your email service. You will need to know this information if you are planning to set up an email client such as Thunderbird, Outlook, or Eudora to access your email.