A catch-all email mailbox receives messages sent to nonexistent addresses under the very same domain. For instance, an email sent to the mistyped email@example.com will be delivered to firstname.lastname@example.org in case 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 typo or to an obsolete one, which they may still have, but you have already deactivated. Only one mailbox per domain name can be a catch-all one and email forwarding cannot be set up for such a mailbox. This is so because of the fact that at some point you may begin receiving spam emails in the catch-all mailbox and the forwarding restriction means that the spam will not be re-sent to a 3rd-party mailbox.