Overview
The H
header configuration
file command tells sendmail which
headers are required for inclusion in the header portion of
mail messages. Some headers, such as Date
:, are added only if
one is not already present. Others, such as Received:
(Received: on page 1162), are added
even if one or more are already present.
The form for the header command is:
H?flags?name:field
The H
must begin the line.
The optional ?flags
?
(the question marks are
literal), if present, must immediately follow the H
with no intervening
space. We will discuss header
?flags
?
after the
name
and
field
are
explained.
The name
is the name of the header,
such as From
. The
name
must immediately
follow the ?flags
?
, if present, or the
H
if there are no
flags.
A colon then follows, which can be surrounded by optional
space characters. The field
is
last and constitutes everything from the first nonspace
character following the colon to the end of the line:
Hname : field ↑ from here to end of line is the field
The colon must be present. If it is absent,
sendmail prints the following
error message and ignores that H
command:
header syntax error, line "offending H command here"
The "offending H command here" is the
full text of the H
command in the configuration file that caused the
error.
Prior to V8.10 sendmail, the
field
could only be the
text of an ordinary header. Beginning with V8.10, the
field
can also be a
$
> or
$
+> operator
(Rules Check Header Contents on page 1130) followed by the name or number of a rule set through ...
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