POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail, probably using POP3.

SMTP stands for Simple Mail Transfer Protocol. SMTP is used to send mail from one server to another. If you look in your email preferences file (check Tools in Outlook Express) you will see that your SMTP server is listed where it says "outgoing mail server". Generally, SMTP accounts are provided by your ISP. Hosting companies usually only provide POP mail -- receiving mail from your domain name.