SMTP, POP3, and IMAP

When configured for TCP/IP networking, an OpenVMS system can act as a POP3, IMAP and SMTP server. Any computer system with an appropriate e-mail client application (e.g., a personal computer running Microsoft Outlook Express) can be used as a client system. POP3 (Post Office Protocol Version 3) is a protocol for retrieving mail messages from the server, eventually deleting them from the server. IMAP (Internet Message Access Protocol) is similar in function to POP3, but stores messages on the server rather than on the client. SMTP (Simple Mail Transfer Protocol) is used to send outgoing messages from the client.

Incoming Internet messages are received by the OpenVMS system, which places the message in the mail file for the proper user. Each user has a mail file located in his login directory. The primary file is called MAIL.MAI, but other files, also of the .MAI type, are created and deleted automatically as needed.

At intervals, the client system logs in to the OpenVMS system (via POP3 or IMAP) and checks to see whether new messages exist. The client uses the same username and password that the user does when logging in interactively. If any new messages exist, the client either downloads them (in the case of POP3) or stores them in the appropriate OpenVMS message store folder (in the case of IMAP).

For outgoing messages, the client connects directly to the SMTP server software on the OpenVMS system and transmits the message. The SMTP server, in turn, forwards the message toward its eventual destination. The message is never stored in the user's .MAI files.

To configure POP3/IMAP/SMTP client software, you will need to know the following things: your username, your password, the name or network address of the OpenVMS server system, the TCP/IP port on which each service is running, and your Internet-format e-mail address as described above. Your system manager can supply each of those items.

If you use OpenVMS mail though a client system, your system manager will probably disable the new-mail notifications that would normally appear when you log in interactively.