You offer hosting. Why are you using a free email service still? Run your own email server.
Where do you get those numbers from? Last time I knew, postfix and qmail were both free?
I use both, both have their advantages & disadvantages. I personally prefer Hotmail because I use MSN and I also have it fully integrated into my WP7, and of-course use it for Zune, Xbox Live etc etc.
I also use Google for more business orientated email, but don't use Google Apps as of yet.