A catch-all mailbox receives email messages sent to invalid addresses under the very same domain name. For instance, an email sent to the mistyped firstname.lastname@example.org will be delivered to email@example.com in case the catch-all feature has been activated for the latter. Thus, you can get messages from pals or customers who may have sent a message to your email address with a spelling mistake or to an old 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 set up for such a mailbox. The latter is due to the fact that at some moment you may begin receiving spam messages in the catch-all mailbox and the forwarding limitation means that the spam will not be delivered to a 3rd-party mailbox.