Sun Microsystems Sun Workstation 100U System Manager's Manual page 318

SENDMAIL
a
sender-l
sender-2
sender-3
L j
:1
.,
r
sendmail
...J l
r
. .
mailer-l
mailer-2
mailer-3
Figure 1 - Sendmail System Structure.
which routes the message to the correct mailer(s). Since some of the senders may
be
network
servers and some of the mailers may
be
network clients,
sendmail
may be used as an internet
mail gateway.
2. OVERVIEW
2.1. System Organization
Sendmail
neither interfaces with the user nor does actual mail delivery. Rather, it
collects a message generated by a user interface program (UIP) such as Berkeley Mail, MS
[Crocker77b], or MH [Borden79), edits the message as required by the destination network,
and calls appropriate mailers to do mail delivery or queueing for network transmission
l
.
This discipline allows the insertion of new mailers at minimum cost. In this sense sendmail
resembles the Message Processing Module fMPM) of (PosteI79bJ.
2.2. Interfaces to the Outside World
There are three ways sendmail can communicate with the outside world, both in
receiving and in sending mail. These are using the conventional UNIX argument
vector/return status, speaking SMTP over a pair of UNIX pipes, and speaking SMTP over
an interprocess(or) channel.
2.2.1.
Argument vector/exit .tatua
This technique is the standard UNIX method for communicating with the process.
A list of recipients is sent in the argument vector, and the message body is sent on the
standard input. Anything that the mailer prints is simply collected and sent back to
the sender if there were any problems. The exit status from the mailer is collected
after the message
is
sent, and a diagnostic
is
printed if appropriate.
iexcept when mailing to
i.
file. when ",,4""Jil does the delivery directly.
Venlon 4.1
DRAFT
L .. t Modl/tO/13