A catch-all mailbox receives email messages sent to non-existent email addresses under the exact same domain name. For example, an email sent to the miswritten suport@domain.com will go to support@domain.com in case the catch-all feature has been enabled for the latter. In this way, you can get email messages from friends or clients who may have sent a message to your email address with a spelling error or to an old one, which they may still have, but you have already disabled. Just one mailbox per domain can be a catch-all one and email forwarding cannot be enabled for such a mailbox. This is due to the fact that at some moment you may begin receiving spam email messages in the catch-all mailbox and the forwarding limitation implies that the spam will not be received in a 3rd-party mailbox.