I suppose I am one of few that does not believe that an email application should try to do everything. I think a good email app is one that just does email, and does it well. I have had way too many problems with Outlook over the years to trust it again.

The perfect email app for me is Qualcomm Eudora. It is super straight-forward, has clarity in its "hedge-hog" concept (Good To Great reference). It also has very powerful filtering and tagging options that include cross-referencing groups of address books for matching AND non-matching, simple context matching (contains, starts with, etc.) as well as Regular Expression matching for the most finely tuned filtering options possible. I use my filterset to eliminate spam without a plugin or third party extension.