POP3 service overview

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

POP3 service overview

The POP3 service is an e-mail service that retrieves e-mail. Administrators can use the POP3 service to store and manage e-mail accounts on the mail server.

When the POP3 service is installed on the mail server, users can connect to the mail server and retrieve e-mail to their local computer using an e-mail client that supports the POP3 protocol (such as Microsoft Outlook). The POP3 service is used with the Simple Mail Transfer Protocol (SMTP) service, which sends outgoing e-mail.

E-mail transfer and retrieval overview

The diagram illustrates how e-mail is transferred from sender to recipient, and how it is then retrieved to the recipient's local computer.

The sender's client computer connects to the Internet through an Internet Service Provider (ISP). Using an e-mail client, the sender sends an e-mail. The e-mail is picked up according to the SMTP protocol and is transferred to the sender's ISP, which then routes the e-mail out onto the Internet.

The e-mail moves through the Internet and is relayed through a varying number of intermediate servers on its way to the recipient. When the e-mail reaches the recipient's ISP, it is dropped into the recipient's mailbox.

When the recipient's computer connects to the recipient's ISP, the e-mail is then transferred from the ISP to the recipient's e-mail client on the local computer, according to the POP3 protocol. The POP3 service is the mechanism that allows users to retrieve their e-mail from the mail server.