A catch-all mailbox receives messages sent to invalid email addresses under the very same domain name. For example, an email message sent to the misspelled 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 get messages 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 deleted. Just 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 point you may begin receiving spam messages in the catch-all mailbox and the forwarding restriction means that the spam will not be sent to a third-party mailbox.