A catch-all email mailbox receives emails sent to inactive email addresses under the very same domain name. For instance, an email sent to the misspelled suport@domain.com will go to support@domain.com if the catch-all feature has been activated for the latter. Thus, you can receive messages from friends or clients who may have sent a message to your email address with a typo or to an old one, which they may still have, but you have already disabled. Just one single mailbox per domain name can be a catch-all one and email forwarding cannot be activated for such a mailbox. The latter is due to the fact that at a certain point you may begin receiving spam emails in the catch-all mailbox and the forwarding restriction means that the spam will not be received in a third-party mailbox.