Sun Microsystems Sun Workstation 100U System Manager's Manual page 323

SENDMAIL
8
unused internally, and can be used as shorthand in the conlguration lie.
3.'1.2. Header deelaratlona
Header declarations inform 8endmtJil of the format of known header lines.
Knowledge or a rew header lines is built into
lendmail,
such as the "From:" and
"Date:" lines.
Most configured headers will be automatically inserted in the outgoing message if
they don't exist in the incoming message. Certain headers are suppressed by some
mailers.
3.'1.3. MaUer deelaratlon.
Mailer declarations tell 8endmtJil of the various mailers available to it. The
definition specifies the internal name of the mailer, the pathname of the program to
call, some 8ags associated with the mailer, and an argument vector
to
be used on the
call; this vector is macro-expanded before use.
3.7.4. Addl'eu
I'ewrltln. rul_
The heart of address parsing in 8endmtJiI is a set of rewriting rules. These are an
ordered list of pattern-replacement rules, (somewhat like a production system, except
that order is critical), which are applied to each address. The address
is
rewritten tex-
tually until it is either rewritten into a special canonical form (i.e., a (mailer, host, user)
3-tuple, such as {arpanet, usc-isif, postel} representing the address "posteIGusc-isif"),
or it falls off the end. When a pattern matches, the rule
is
reapplied until it rails.
The configuration file also supports the editing or addresses into different formats.
For example, an address of the form:
ucsfcgl!tef
might be mapped into:
ter@ucsrcgl.UUCP
to conform to the domain syntax. Translations can also be done in the other direction.
3.'1.5. Option Bettln.
There are several options that can be set from the contiguration tile. These
include the pathnames of various support files, timeouts, default modes, etc.
4. COMPARISON WITH OTHER MAILERS
4.1. DeUvel'maU
Sendmail is an outgrowth of delivermtJiI. The primary differences are:
(1) Configuration information is not compiled in. This change simplifies many of the
problems of moving to other machines. It also allows easy debugging of new mailers.
(2) Address parsing is more 8exible. For example, delivermail only supported one gate-
way to any network, whereas 8endmtJil can be sensitive to host names and reroute to
different gateways.
(3) Forwarding and :include: features eliminate the requirement that the system alias lie
be writable by any user (or that an update program be written, or that the system
administration make all changes).
(4) Sendmail supports message batching acr068 networks when a message is being sent to
multiple recipients.
Venlon 4.1 DRAFT
Last Mod 8/IV/83