A catch-all mailbox receives messages sent to non-existent addresses under the exact same domain name. For instance, a message sent to the mistyped firstname.lastname@example.org will go to email@example.com in case the catch-all feature has been activated for the latter. In this way, you can receive messages from pals or customers who may have sent a message to your email address with a typo or to an outdated one, which they may still have, but you have already deleted.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. The latter is due to the fact that at some point you may start receiving spam emails in the catch-all mailbox and the forwarding limitation means that the spam will not be re-sent to a 3rd-party mailbox.