Technical data

Configuring and Managing SMTP
17.1 Key Concepts
The SMTP symbiont processes all mail on the host. It receives jobs one at a
time from the generic SMTP queue and delivers them either locally by means of
OpenVMS Mail, or remotely by means of SMTP.
The configuration procedure TCPIP$CONFIG sets up the SMTP queues for you.
See Section 17.2 for more information on configuring SMTP.
After receiving a client request, the SMTP server responds, indicating its status
(available or not available). If the server is available, it starts an exchange of
control messages with the client to relay mail. (Like FTP, SMTP does not define a
message format. SMTP commands are sent as ASCII text, and the SMTP server
at the remote host parses the incoming message to extract the command.)
The following steps occur:
1. The auxiliary server listens for requests, starts the SMTP receiver, and
accepts the TCP connection.
2. The client identifies itself by sending its fully qualified domain name.
3. The server replies with its own fully qualified domain name.
4. The client sends the full e-mail address of the sender enclosed in angle
brackets; if the server is able to accept the mail, it returns a readiness code.
5. The client sends the full mail address (also enclosed in angle brackets) of the
message’s intended recipient.
6. The client sends the body of the message.
A minimum of five control message commands are required to conduct the
preceding sequence. Table 17–1 describes these commands.
Table 17–1 SMTP Client Commands
Command Description
HELO Identifies the originating host to the server host. Use
the /DOMAIN qualifier to provide the name of the
originating host.
MAIL FROM:<reverse-path> Identifies the address at which undeliverable mail
should be returned. Usually is the originating host.
RCPT TO:<forward-path> Address of the intended receiver. If sending mail to
multiple recipients, use one RCPT TO command for
each recipient.
DATA Signals the end of the RCPT TO commands and tells
the recipient to prepare to receive the message itself.
QUIT Indicates no more commands.
These commands are described in RFC 821.
17.1.2 Understanding the SMTP Control File
With TCP/IP Services SMTP, each mail message is packaged into a special-
purpose binary file called a control file. This control file is submitted to a generic
SMTP queue to be processed by the SMTP symbiont. Each control file contains
one SMTP mail message. Note that an SMTP message addressed to multiple
recipients is stored in one control file.
Control file names provide information about the mail contained within. The
format for the control file name is as follows:
17–2 Configuring and Managing SMTP