Previous Table of Contents Next  Header Declarations  Header
declarations inform sendmail of the format of known header
lines. Knowledge of a few header lines is built into sendmail,
such as the From: and Date: lines.  Most configured headers are
automatically inserted in the outgoing message if they don't
exist in the incoming message. Certain headers are suppressed by
some mailers.  Mailer Declarations  Mailer declarations specify
the internal name of the mailer, some flags associated with the
mailer, and an argument vector used on the call. This vector is
expanded by a macro before use.  Name-Rewriting Rules  Name-
rewriting rules are the heart of name parsing in sendmail. They
are an ordered list of pattern-replacement rules, which are then
applied to each name. In particular, ruleset 0 determines which
mailer to use. The name is rewritten until it is either
rewritten into a special canonical form — for example, a
{mailer, host, user} triplet, such as {ddn,, postel},
representing the name "" — or until it