A catch-all mailbox receives email messages sent to invalid email addresses under the very same domain. For example, an email sent to the mistyped suport@domain.com will be delivered to support@domain.com in case the catch-all feature has been activated for the latter. In this way, you can get messages from buddies or clients who may have sent a message to your email address with a typographical error or to an out-of-date one, which they may still have, but you have already deleted. Only one single mailbox per domain can be a catch-all one and email forwarding cannot be activated for such a mailbox. This is due to the fact that at some moment you may begin receiving spam email messages in the catch-all mailbox and the forwarding restriction implies that the spam will not be re-sent to a 3rd-party mailbox.