my Apple ID is ...@mac.com -- can I use it with iCloud?
According to apple's FAQ (you can find it here:http://www.apple.com/mobileme/transition.html)


  Can I keep my MobileMe email address once I move to iCloud? Yes. If
  you have an active MobileMe account when you sign up for iCloud, you
  can keep your me.com or mac.com email address and any email aliases
  you have created and move your MobileMe mail, contacts, and calendars,
  as well as your bookmarks, to the new service. When you're ready to
  make the move, go to www.me.com/move.


You can try to move your emails to iCloud by visiting me.com/move