A catch-all mailbox receives messages sent to invalid email addresses under the very same domain. For instance, a message sent to the mistyped firstname.lastname@example.org will be delivered to email@example.com if the catch-all feature has been activated for the latter. Thus, you can receive messages from buddies or clients who may have sent a message to your email address with a typographical error or to an old one, which they may still have, but you have already deactivated. Just one mailbox per domain name 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 a certain moment you may begin receiving spam messages in the catch-all mailbox and the forwarding limitation means that the spam will not be redirected to a 3rd-party mailbox.