What you ask for, Kevin, may already be present.  To some exent it depends
upon the user's mail system an personal preferences.  Last time I checked,
the options, setable by the user, were:

DIGEST
DIGEST MIME
DIGEST HTML
DIGEST MIME HTML

Personally, with my preferences (including email system) I have no use for
anything other than plain DIGEST,  but some like the other setings, and
some curse them to the bad place.

Douglas Winship     [log in to unmask]