At long last (and about 3 months past due, says my OmniFocus) I have released a new stable release of Email::Abstract. This release should be significantly saner, with better facilities for a plugin to declare when it will work and when it should be ignored.
Email::Abstract is likely to be the email representation passed around in Email::Sender, which should be the next thing to get some attention. Please let me know if you have any problems or concerns about it. -- rjbs