Force close on 'Email' app when opening mail

When you're having trouble with the various email apps, the first thing to try is to clear the cache and (if possible) the data through "Manage Applications." These apps tend to get "constipated" or confused by a corrupt message they are storing.

P.S. It's also a good idea to filter your apps to "All" in the Manage Applications settings. Some apps, such as gmail, have a separate "storage" app (at least in 2.1) that you cannot see without filtering for all apps.