H header configuration file command tells
sendmail which headers are required for
inclusion in the header portion of mail messages. Some headers, such
Date:, are added only if one is not already
present. Others, such as
Received: (Received:), are added even if one or more are already
The form for the header command is:
H must begin the line. The optional
? (the question
marks are literal), if present, must immediately follow the
H with no intervening space. We will discuss
field are explained.
name is the name of the header, such
immediately follow the
?, if present, or
H if there are no flags.
A colon then follows, which can be surrounded by optional space
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
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
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
$+> operator (Section 25.5) followed by the name or number of a rule set through which the header’s value is to ...