Email Basics

When you send and receive email messages over the Internet, your email client software on the PC or on the phone primarily needs to communicate with two types of email servers over the TCP/IP protocol:

Simple Mail Transport Protocol (SMTP) server
Takes email messages from your email client and sends them to the recipient's email server. To avoid being exploited by spammers, most SMTP servers require you to have an account with them and to authenticate yourself before you can send an email message.

POP or IMAP servers
Give you access to your email accounts. Your email client software logs into the POP or IMAP server periodically, using your username and password, to check for and retrieve new messages.
Typically, your SMTP and POP/IMAP servers are hosted by your Internet Service Provider (ISP) or by your company's IT department. If you use web mail (e.g., Yahoo! Mail and Hotmail), you typically need to pay for the privilege to directly access their mail servers.

An open source program called YPOPs emulates a POP3 account over your free Yahoo! Mail account on your own computer. For more information, visit http://yahoopops.sourceforge.net/.