What is the best project management software?

Here are basic things it needs to have:

Customizable

Group Management

Document Management

Email Management

Either a Lease or a big Licensing for 400+ users.What is the best project management software?
I have used Base Camp for a few years now and have not yet found one thing yo complain about yet:

http://basecamphq.com/



It covers all your requirements and much more.What is the best project management software?
Recently I have brought Content Central from Ademero for Document Management you can also try this because this product is easy to use, it has a professional-looking interface, it is excellent compared to other programs in this section and so on.