A catch-all mailbox receives emails sent to nonexistent email addresses under the very same domain. For example, an email message sent to the misspelled firstname.lastname@example.org will go to email@example.com if the catch-all feature has been enabled for the latter. Thus, you can receive emails from buddies or customers who may have sent a message to your email address with a spelling error or to an old one, which they may still have, but you have already deleted. Only one 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 restriction means that the spam will not be sent to a 3rd-party mailbox.