so it's not integrated with the mailer; but at least it's not web-based, and
it looks like it's fairly functional.

http://www.favorin.com/products/time/screenshots.shtml

client appears to be free, and is usable for personal calendaring; calendar
server is payware, and lets you schedule between people.
at least that's how I read their blurb on Freshmeat.

Carl Soderstrom.
-- 
Systems Administrator
Real-Time Enterprises
www.real-time.com