A catch-all email mailbox receives messages sent to non-existent addresses under the same domain. For example, a message sent to the misspelled 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 get emails from colleagues or customers who may have sent a message to your email address with a spelling mistake or to an obsolete 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 due to the fact that at a certain point you may start receiving spam emails in the catch-all mailbox and the forwarding restriction implies that the spam will not be delivered to a 3rd-party mailbox.