additional to http://bugs.gentoo.org/show_bug.cgi?id=46842 i'd like to add this patch: http://home.uchicago.edu/~dgc/mutt/#attach it's an attachment-counting patch, that allows you to have the number of attachments of an email show up in the index.
This is a pretty large patch which hasn't been updated since mutt 1.5.1. Thanks anyway, I'd rather wait for this feature to appear in mutt upstream instead.