The POP3 service

POP3 (Post Office Protocol Version 3) is an Internet mail protocol that allows a user running a POP3 client -- for example, the Notes® POP3 client, Eudora Pro, or Microsoft Outlook Express® -- to retrieve mail from a server that runs the POP3 service. You can set up a Domino® server to run the POP3 service. The Domino® server receives and stores mail for POP3 users, who can then connect to the server to retrieve their mail.

The Domino® POP3 service acts as an intermediary for communications between POP3 mail clients and the Domino® mail server. By default, the Domino® POP3 service monitors TCP port 110, where POP3 clients connect to submit requests to the service to retrieve mail. After receiving a request, the POP3 service sends mail to the client. POP3 clients let users specify whether to leave a copy of a message on the server after retrieving it. By default, messages downloaded by the client are deleted from the server.

The POP3 service complies with RFC 1939 - Post Office Protocol Version 3.

Supporting outbound mail service for POP3 clients

POP3 is a mail access protocol only and does not stipulate any method for sending mail. To ensure that POP3 clients can send outbound mail, you must provide them with access to an SMTP server. The SMTP server can be the Domino® server running the POP3 service, another Domino® server, or a non-Domino SMTP server.

Authenticating with the server

The Domino® server does not check Notes® User ID files to verify the identity of users who connect from a POP3 client. Because the POP3 service does not use ID files to identify users and control access to servers, a POP3 user does not have to be a registered Notes® user. To access mail through the POP3 service, users need a mail file on the server and a Person document (including an Internet password) in the Domino® Directory. Only users who receive encrypted Notes® mail or access Domino® applications must be registered Notes® users.

To authenticate POP3 users, Domino® relies on authentication methods built into the Internet protocols. The methods available depend on the server ports you configure the POP3 service to use. The POP3 service can use a TCP/IP port, a TLS port, or both the TCP/IP and TLS ports.

If POP3 uses the TCP/IP port only (the default), the server uses basic name-and-password authentication to identify users. The login names that the server accepts as valid depend on the setting in the Internet authentication field on the Security tab of the Server document.

If the TLS port is enabled, you can specify whether a client certificate is required to authenticate (TLS authentication), and whether clients must also supply a name and password.

Accessing a mail file from the Notes® client and a POP3 client

POP3 clients use the standard Domino® mail file database. This allows registered Notes® users to access their mail files from both a POP3 client and the Notes® mail client.