A catch-all email mailbox receives emails sent to invalid addresses under the same domain. For example, a message sent to the mistyped suport@domain.com will go to support@domain.com in case the catch-all feature has been enabled for the latter. In this way, you can get emails from colleagues or clients who may have sent a message to your email address with a typo or to an obsolete one, which they may still have, but you have already disabled. 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 a certain moment you may begin receiving spam email messages in the catch-all mailbox and the forwarding limitation implies that the spam will not be received in a third-party mailbox.