> Ability to specify only a part of the message as "preformatted text", so they don't get word-wrapped. Useful for pasting console output in support messages, for example.
Do you mean when writing mails or viewing them? Mutt takes whatever $EDITOR gives back, verbatim. For viewing, I have bindings to toggle between 78 width and $COLUMNS-2 (300+ here which is a little much for a default wrap boundary).
> Nice "bullet list"/"number list" support.
I tend to just do ASCII lists in vim myself.
> Pretty good IMAP support.
I use offlineimap here.
> Multiple-language spell-checking in a single mail.
I'm not bilingual (or anything more for that matter), so I've not had to solve this one.