A catch-all functionality that is activated for a certain mailbox will allow you to receive email messages that are sent to addresses that do not really exist. Otherwise put, if you delete an email address and somebody still sends a message to it, or to any miswritten address under the same domain name, you’ll get the email in the catch-all mailbox. Using this functionality implies that you will no longer miss an email for any reason whatsoever, which could be essential in case you are running some business, for instance. Since you may begin receiving spam emails, you can combine the catch-all option with email filters in order to receive only legitimate messages in your inbox. Just one single mailbox per domain can be a catch-all one and email forwarding cannot be set up for a catch-all mailbox.