=o= MH doesn't have an automatic signature mechanism, but it
is so configurable that there are a number of different ways
to implement one.  Check the periodic "MH Frequently Asked
Questions (FAQ) with Answers" posting for details.

=o= CAVEAT:  If you use the environment variable SIGNATURE to
point to your signature file, MH will use it not as a signature,
but as your "fullname".  Even worse, if your version of MH was
built with the "UCI" option and you *don't* use the environment
variable SIGNATURE to point to another file, MH will use the
$HOME/.signature file for this purpose!  To see if your version
of MH has this behavior, enter this command:

  % send -help

And look for the string "[UCI]" in the output.

=o= There's an Emacs interface to MH, called MH-E.  It has its
own signature mechanism, which is invoked with the "mh-insert-
signature" command (bound to the "C-c C-s" keys by default).

=o= This will insert the file $HOME/.signature file by default.
If your signature file has another name (e.g., to avoid its
being used by an MH build with the "UCI" option), you can set
the "mh-signature-file-name" variable to refer to a different
file.