Chris Shaddock wrote:
I uncovered an old @mac.com email I haven't moved over to MobileMe.
You never had to move an @mac.com address - it continued working alongside the @me.com address when that was introduced, provided you haven't allowed the account to expire between then and last June.
If your MobileMe account had both versions and you have migrated at http://me.com/move , then signed in with your MobileMe email address at System Preferences>iCloud (Lion 10.7.2 required) and checked 'Mail' in the list, then both addresses should work and deliver into the same inbox.
If you have a pre-Lion system you will need to set Mail up manually:
If you had a different @mac.com address and allowed it to expire then it's gone.