A catch-all email mailbox receives emails sent to invalid email addresses under the exact same domain name. For example, an email 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. Thus, you can get emails from colleagues or clients who may have sent a message to your email address with a typographical error or to an outdated one, which they may still have, but you have already disabled.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 enabled for such a mailbox. This is due to the fact that at some point you may start receiving spam messages in the catch-all mailbox and the forwarding limitation means that the spam will not be received in a third-party mailbox.