Sendmail Installation and Operation Guide
SMM:08-77
5.7. P -- Precedence Definitions
Values for the "Precedence:" field may be defined using the P control line. The syntax of this
field is:
Pname=num
When the name is found in a "Precedence:" field, the message class is set to num. Higher numbers
mean higher precedence. Numbers less than zero have the special property that if an error occurs
during processing the body of the message will not be returned; this is expected to be used for
"bulk" mail such as through mailing lists. The default precedence is zero. For example, our list of
precedences is:
Pfirst-class=0
Pspecial-delivery=100
Plist=-30
Pbulk=-60
Pjunk=-100
People writing mailing list exploders are encouraged to use "Precedence: list". Older versions of
sendmail (which discarded all error returns for negative precedences) didn't recognize this name,
giving it a default precedence of zero. This allows list maintainers to see error returns on both old
and new versions of sendmail.
5.8. V -- Configuration Version Level
To provide compatibility with old configuration files, the V line has been added to define
some very basic semantics of the configuration file. These are not intended to be long term sup-
ports; rather, they describe compatibility features which will probably be removed in future releases.
N.B.:
these version levels have nothing to do with the version number on the files. For exam-
ple, as of this writing version 10 config files (specifically, 8.10) used version level 9 configurations.
"Old" configuration files are defined as version level one. Version level two files make the
following changes:
(1)
Host name canonification ($[ ... $]) appends a dot if the name is recognized; this gives the
config file a way of finding out if anything matched. (Actually, this just initializes the
"host" map with the "-a." flag -- you can reset it to anything you prefer by declaring the
map explicitly.)
(2)
Default host name extension is consistent throughout processing; version level one configu-
rations turned off domain extension (that is, adding the local domain name) during certain
points in processing. Version level two configurations are expected to include a trailing dot
to indicate that the name is already canonical.
(3)
Local names that are not aliases are passed through a new distinguished ruleset five; this can
be used to append a local relay. This behavior can be prevented by resolving the local name
with an initial `@'. That is, something that resolves to a local mailer and a user name of
"vikki" will be passed through ruleset five, but a user name of "@vikki" will have the `@'
stripped, will not be passed through ruleset five, but will otherwise be treated the same as
the prior example. The expectation is that this might be used to implement a policy where
mail sent to "vikki" was handled by a central hub, but mail sent to "vikki@localhost" was
delivered directly.
Version level three files allow # initiated comments on all lines. Exceptions are backslash
escaped # marks and the $# syntax.
Version level four configurations are completely equivalent to level three for historical rea-
sons.