When e-mail messages are sent to an address under your domain that does not exist, you can choose to redirect them to a single address, also known as a catchall.
Go to the "Mail" tab.
Click "Change Settings".
Choose "Forward to Address".
Type the address where you want the mail to be sent.
Click "OK".
That's it! The catchall e-mail has been setup, and whenever a message is sent to a non-existant address on your domain, it will be re-routed to the new address we specified.