A catch-all mailbox receives email messages sent to non-existent addresses under the very 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. Thus, you can get email messages from mates or customers who may have sent a message to your email address with a typographical error or to an out-of-date one, which they may still have, but you have already deactivated. Only one single mailbox per domain name can be a catch-all one and email forwarding cannot be set up for such a mailbox. This is so because of the fact that at a certain point you may start receiving spam messages in the catch-all mailbox and the forwarding restriction implies that the spam will not be redirected to a 3rd-party mailbox.