mh-decode-mime-flag

mh-decode-mime-flag is a variable defined in `mh-e.el'.
Its value is

t

Documentation:
*Non-nil means attachments are handled.

MH-E can handle attachments as well if the Gnus `mm-decode'
library is present. If so, this option will be on. Otherwise,
you'll see the MIME body parts rather than text or attachments.
There isn't much point in turning off this option; however, you
can inspect it if it appears that the body parts are not being
interpreted correctly or toggle it with the command
; to view the raw message.

This option also controls the display of quoted-printable
messages and other graphical widgets. See the options
`mh-graphical-smileys-flag' and `mh-graphical-emphasis-flag'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 7.0 of the MH-E package that is part of Emacs 22.1.