mh-display-buttons-for-alternatives-flag

mh-display-buttons-for-alternatives-flag is a variable defined in `mh-e.el'.
Its value is

nil

Documentation:
*Non-nil means display buttons for all alternative attachments.

Sometimes, a mail program will produce multiple alternatives of
the attachment in increasing degree of faithfulness to the
original content. By default, only the preferred alternative is
displayed. If this option is on, then the preferred part is shown
inline and buttons are shown for each of the other alternatives.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 7.4 of the MH-E package that is part of Emacs 22.1.