In cPanel you can forward an entire domain to another by using the 'email domain forwarder' option.

If you have a .co.uk domain as a parked domain on top of your .com domain for instance, you can use this to forward something@yourdomain.co.uk to something@yourdomain.com, and so on.

Obviously the likelihood of this happening is quite small, and for the sake of spam reduction we'd generally suggest you actually setup only the forwarders you need under emails - > forwarders.