That would be a lot trickier. I was thinking more along the lines of the usual "you have new messages in BattleMaster" notification.
Actually, I've implemented something along those lines before. Provided you have cooperative email server software, it can work pretty well.
In this case, we would probably want to implement it along the lines of the ones that have auto-generated email addresses for each message or conversation, with a hash in the actual recipient address (or at least after the +) so that it gets into the right message stream.
Certainly, it's trickier than a simple "you have new messages" notification, but it's far from impossible.
