A catch-all mailbox receives messages sent to inactive addresses under the very same domain. For example, a message sent to the miswritten firstname.lastname@example.org will go to email@example.com in case the catch-all feature has been activated for the latter. In this way, you can get emails from buddies or clients who may have sent a message to your email address with a spelling mistake or to an obsolete one, which they may still have, but you have already deactivated. Only one single mailbox per domain 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 a certain moment you may begin receiving spam email messages in the catch-all mailbox and the forwarding limitation means that the spam will not be redirected to a third-party mailbox.