A catch-all functionality that is enabled for a specific mailbox will permit you to receive email messages that are sent to addresses that do not actually exist. In other words, if you deactivate an email address and somebody still sends a message to it, or to any mistyped address under the same domain, you’ll get the message in the catch-all mailbox. Using this functionality implies that you won’t miss an email for any reason whatsoever, which could be essential in case you are running a business, for example. Since you may start receiving unsolicited bulk messages, you can use the catch-all functionality with email filters in order to receive only legitimate messages in your inbox. Just one mailbox per domain can be a catch-all one and email forwarding cannot be activated for a catch-all mailbox.