For Exchange, we use Exchange. Somewhere in the 25,000-50,000 users area. I use Google Apps for your Domain for my personal domain (zibnet.us) and it works great. Google apps is great for under 50 users. Free, very acceptable web views, syncs with iCal, Outlook, whatever... -- Andrew S. Zbikowski | http://andy.zibnet.us IT Outhouse Blog Thing | http://www.itouthouse.com