A catch-all mailbox receives email messages sent to inactive addresses under the same domain. For example, an email sent to the miswritten suport@domain.com will go to support@domain.com if the catch-all feature has been activated for the latter. Thus, you can get messages from acquaintances or customers who may have sent a message to your email address with a typographical error or to an old one, which they may still have, but you have already deactivated. Only one single mailbox per domain can be a catch-all one and email forwarding cannot be activated for such a mailbox. This is so because of the fact that at some point you may start receiving spam messages in the catch-all mailbox and the forwarding restriction means that the spam will not be redirected to a third-party mailbox.