Another in a long list of productivity enhancements I have tried, MailTags actually worked by allowing me to connect Apple Mail to iCal, something that Apple should have done in the first place. I haven’t tried this latest release as I am still using Tiger but I haven’t found Apple mail to be fast enough for robust email management anyway. Gmail is far faster. Your mileage may vary.
Indev’s MailTags 2.2 is a plug-in for Apple Mail that enables metadata tagging of email. This release adds compatibility with Leopard’s Mail 3.0 (including tagging of notes and RSS items) and also introduces a modular architecture for future enhancements.