A catch-all email mailbox receives messages sent to nonexistent email addresses under the same domain. For example, an email sent to the misspelled firstname.lastname@example.org will be delivered to email@example.com if the catch-all feature has been enabled for the latter. Thus, you can get emails from acquaintances or customers who may have sent a message to your email address with a spelling error or to an out-of-date one, which they may still have, but you have already disabled. Only one 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 some moment you may start receiving spam email messages in the catch-all mailbox and the forwarding limitation implies that the spam will not be re-sent to a 3rd-party mailbox.