Free Email or at least Email Forwarding
Not all clients need or want email accounts, especially Rackspace which costs more. We need a "free" alternative like most hosts provide.
Just to be able to forward emails without having to use the domain registrar would be very helpful.
For example a client who pays me the absolute minimum for his one page promotion site won't want to pay for Rackspace email, he just needs a basic email or forwarder to fire emails over to his gmail or work email.
Ben Gill commented
Please add this!
It's the last pieces of the puzzle for you to become a complete hosting provider.