A catch-all email mailbox receives email messages sent to invalid addresses under the exact same domain. For example, a message sent to the mistyped 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 email messages from pals or customers who may have sent a message to your email address with a spelling error or to an out-of-date one, which they may still have, but you have already deleted. Just one single mailbox per domain can be a catch-all one and email forwarding cannot be enabled for such a mailbox. The latter is due to 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 delivered to a third-party mailbox.