A catch-all mailbox receives emails sent to non-existent email addresses under the same domain. For example, an email sent to the miswritten email@example.com will be delivered to firstname.lastname@example.org in case the catch-all feature has been enabled for the latter. In this way, you can receive email messages from colleagues or customers who may have sent a message to your email address with a typo or to an outdated one, which they may still have, but you have already disabled. Only one mailbox per domain can be a catch-all one and email forwarding cannot be set up 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 limitation implies that the spam will not be redirected to a 3rd-party mailbox.