mh-mml-method-default

mh-mml-method-default is a variable defined in `mh-e.el'.
Its value is

"pgpmime"

Documentation:
Default method to use in security tags.

This option is used to select between a variety of mail security
mechanisms. The default is "PGP (MIME)" if it is supported;
otherwise, the default is "None". Other mechanisms include
vanilla "PGP" and "S/MIME".

The `pgg' customization group may have some settings which may
interest you (see Info node `(pgg)').

In particular, I turn on the option `pgg-encrypt-for-me' so that
all messages I encrypt are encrypted with my public key as well.
If you keep a copy of all of your outgoing mail with a "Fcc:"
header field, this setting is vital so that you can read the mail
you write!

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.