A catch-all email mailbox receives email messages sent to inactive addresses under the exact same domain name. For instance, an email message sent to the miswritten firstname.lastname@example.org will be delivered to email@example.com in case the catch-all feature has been enabled for the latter. Thus, you can get emails 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 deleted. Only one 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 email messages in the catch-all mailbox and the forwarding restriction implies that the spam will not be redirected to a 3rd-party mailbox.