A catch-all mailbox receives messages sent to non-existent email addresses under the exact same domain. For example, an email message sent to the mistyped firstname.lastname@example.org will go to email@example.com if the catch-all feature has been activated for the latter. In this way, you can receive email messages from friends or clients who may have sent a message to your email address with a spelling error or to an outdated one, which they may still have, but you have already deleted. Just one single mailbox per domain name can be a catch-all one and email forwarding cannot be activated for such a mailbox. This is so because of the fact that at some moment you may begin receiving spam messages in the catch-all mailbox and the forwarding restriction implies that the spam will not be redirected to a 3rd-party mailbox.