A catch-all (default) email address in cPanel is an address that will 'catch' any mail that is sent to an invalid email address for your domain. All mail that is sent to an address that does not exist will be send to the default address.

1. Login to cPanel.
2. Click the Default Address icon.
3. Set the "Send all unrouted e-mail for" to the appropriate domain name.
4. In the "Forward to email address" field enter the email address you with to receive all of the emails.
5. Click Change.

In the event you wish to have all emails which aren't directed to a created email account, you may instead set cPanel to "Discard with error to sender (at SMTP time)" within the Default Address area.