A catch-all mailbox receives messages sent to non-existent addresses under the very same domain name. For instance, an email sent to the miswritten 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you can receive messages from buddies or clients who may have sent a message to your email address with a typo or to an out-of-date one, which they may still have, but you have already deactivated. Only one single mailbox per domain name 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 some moment you may start receiving spam emails in the catch-all mailbox and the forwarding restriction means that the spam will not be redirected to a third-party mailbox.