The ability to provide e-mail services to clients includes two critical functions: SMTP and POP3. Together, they provide the means for clients to send outgoing mail and check for new incoming mail, respectively.
POP3 service is the side of e-mail that allows clients to check for new incoming messages delivered to their POP3 e-mail accounts. The POP3 server performs two basic but important functions. First, it authenticates, or verifies, the identity of those trying to access certain POP3 accounts in the form of a login and password. Secondly, it allows clients to download any new e-mail they may have in their POP3 account(s).
Think of the POP3 server in terms of your local post office. Just like snail mail, e-mail is routed in a similar fashion. Access to the mail requires authentication, whether in the form of a lock and key or login and password. Once authentication is verified, one can obtain any mail that might exist (in the PO Box or the POP3 account).
Finally, you need to configure your e-mail client so that it knows what POP3 server to check for new e-mail. This "address" is similar to a unique address you would go to check your mail at a local post office. The same key would not work for the same box number in a different city, just like the same login and password would not work for the same POP3 account on a different POP3 server.
In order to access the correct POP3 server, configure your e-mail client to access the POP3 (Incoming Mail) Server: mail.yourdomain.com.
