Technical data

Conﬁguring and Managing SMTP

The Simple Mail Transfer Protocol (SMTP) is a standard protocol that provides

a reliable and efﬁcient mail delivery system between systems communicating in

a TCP/IP network. SMTP speciﬁes the format of control messages sent between

two machines to exchange electronic mail, but it does not specify the mail

interface.

The TCP/IP Services product implements SMTP as an OpenVMS symbiont that

works with the OpenVMS Mail utility.

This chapter reviews key concepts and describes:

• How to conﬁgure SMTP (Section 17.2)

• How to create a local alias ﬁle (Section 17.3)

• How to manage SMTP (Section 17.4)

• How to modify the SMTP conﬁguration (Section 17.5)

• How to conﬁgure the SMTP antiSPAM feature (Section 17.6)

• How to manage the SMTP send-from-ﬁle (SFF) feature (Section 17.7)

• How to disable the SMTP outbound alias feature (Section 17.8)

• How to solve SMTP problems (Section 17.9)

See the DIGITAL TCP/IP Services for OpenVMS User’s Guide for information

about using SMTP to send and receive mail.

17.1 Key Concepts

To be reliable, electronic mail systems must be able to cope with situations where

the recipient is temporarily unavailable, for example, if the recipient’s host is

down or off line. Mail must also be able to handle situations where some of the

recipients on a distribution list are available and some are not.

SMTP is a store-and-forward mail protocol that accepts mail from an originating

host and forwards it through one or more intermediate hosts before it reaches

its ﬁnal destination. Note that this behavior differs from OpenVMS Mail, where

mail is sent directly from the originating node to the destination node.

17.1.1 How SMTP Clients and Servers Communicate

In most implementations, SMTP servers listen at port 25 for client requests. In

the TCP/IP Services implementation of SMTP, the SMTP receiver is invoked by

the auxiliary server when an inbound TCP/IP connect comes in to port 25 (if the

SMTP service is enabled). The auxiliary server runs the command procedure

speciﬁed in the SMTP service database entry that runs the receiver. The receiver

image is SYS$SYSTEM:TCPIP$SMTP_RECEIVER.EXE. The receiver process

runs in the TCPIP$SMTP account.

Conﬁguring and Managing SMTP 17–1