A catch-all email mailbox receives emails sent to invalid email addresses under the very same domain. For instance, an email sent to the mistyped firstname.lastname@example.org will go to email@example.com in case the catch-all feature has been enabled for the latter. In this way, you can receive emails from friends 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 deactivated. Only one mailbox per domain name can be a catch-all one and email forwarding cannot be enabled for such a mailbox. This is so because of the fact that at a certain moment you may begin receiving spam email messages in the catch-all mailbox and the forwarding limitation means that the spam will not be redirected to a 3rd-party mailbox.