A catch-all feature that is enabled for a given email mailbox will permit you to receive email messages that are sent to email addresses that do not actually exist. To put it differently, if you deactivate an email address and someone still sends a message to it, or to any misspelled email address under the very same domain, you will get the email in the catch-all mailbox. Using this feature means that you will no longer miss an email for any reason whatsoever, which could be essential in case you run a business, for instance. Since you may start receiving spam emails, you can use the catch-all feature with anti-spam filters so as to receive only legitimate email messages in your inbox. Just one single mailbox per domain can be a catch-all one and email forwarding cannot be activated for a catch-all mailbox.