because every single mail plug-in is an unofficial hack. Apple does not support plug-ins for mail. Why? Probably because Apple loves closed source and money. They don't stand for openness at all.

They don't support plug-ins because it's not their job to. Apple provides a method for these plugins to work, but it's not their job to make sure developers update their plugins to work with new version of Mail. This app does what each developer should be doing on their own - which is simply doing a 5-second copy/paste job on the plist file.

I'm not so sure. Thunderbird supports plug-ins, right? Apple Mail does not. Now do the math. Of course Apple doesn't have to do anything. I'm just saying Apple Mail is not supporting plug-ins, which prevents good plug-ins to be developed since that is a real pita, because nothing is documented. And since the original poster was talking about mail, I thought I'd add that info, that all mail-plug-ins are hacks.