1. Ability to access my mail through different computers
2. Ability to access my addresses through different computers
3. Ability to use whatever email client I wish
4. Ability to keep copies of sent messages
5. Ability to consolidate all my different mail accounts, and run run filters on them (spam filters)
6. Ability to respond to XML-RPC or SOAP requests, to count the number of messages, or other things (query for a specific sender, maybe???)
7. Ability to send off emails at certain times. Weather, News. Or delay email messages.

And THAT would be a nice server :-)