mh-mhl-format-file

mh-mhl-format-file is a variable defined in `mh-e.el'.
Its value is

nil

Documentation:
*Specifies the format file to pass to the "mhl" program.

Normally MH-E takes care of displaying messages itself (rather than
calling an MH program to do the work). If you'd rather have "mhl"
display the message (within MH-E), change this option from its default
value of "Use Default mhl Format (Printing Only)".

You can set this option to "Use Default mhl Format" to get the same
output as you would get if you ran "mhl" from the shell.

If you have a format file that you want MH-E to use, you can set this
option to "Specify an mhl Format File" and enter the name of your
format file. Your format file should specify a non-zero value for
"overflowoffset" to allow MH-E to parse the header. Note that
"mhl" is always used for printing and forwarding; in this case, the
value of this option is consulted if you have specified a format
file.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 8.0 of the MH-E package that is part of Emacs 22.1.