A catch-all mailbox receives email messages sent to nonexistent addresses under the very same domain name. For instance, an email message sent to the mistyped firstname.lastname@example.org will go to email@example.com in case the catch-all feature has been enabled for the latter. Thus, you can get messages from partners or customers who may have sent a message to your email address with a typo or to an outdated one, which they may still have, but you have already deactivated. Just 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 moment you may start receiving spam emails in the catch-all mailbox and the forwarding limitation implies that the spam will not be sent to a 3rd-party mailbox.