Comments provide you with the documentation necessary to maintain the configuration file. Because comments slow sendmail down by only a small amount, it is better to overcomment than to undercomment.
Blank lines and lines that begin
with a #
character are considered comments and are ignored.
A blank line is one that contains no characters at all (except for
its terminating newline). Indentation characters (spaces and
tabs) are invisible and can turn
an apparently blank line into an empty-looking line, which is
not ignored:
# text a comment tabtext a continuation line a blank line tab an "empty-looking line"
Except for V8 sendmail and two special cases, comments
occupy the entire line. The two special cases are the R
and S
configuration commands.
The R
command is composed
of three tab-separated fields, the third field being a comment that
does not require a leading #
character:
Rlhs rhs comment
The pre-V8.7 S
command looks only for a number following it and
ignores everything else, so it may also be followed by a comment:
S3 this is a comment
No other commands allow comments to follow on the same line:
CWlocalhost mailhost # This won't work prior to V8