A catch-all mailbox receives messages sent to nonexistent addresses under the same domain. For instance, an email sent to the miswritten suport@domain.com will go to support@domain.com in case the catch-all feature has been enabled for the latter. Thus, you can receive messages from buddies or clients 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 single mailbox per domain name 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 emails in the catch-all mailbox and the forwarding limitation means that the spam will not be delivered to a third-party mailbox.