A catch-all functionality that is activated for a specific mailbox will permit you to receive email messages that are sent to email addresses that do not really exist. Otherwise put, if you deactivate an email address and somebody still sends an email to it, or to any miswritten email address under the same domain, you will 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 crucial if you run a company, for instance. Since you may start receiving unsolicited email messages, you can combine the catch-all functionality with anti-spam filters in order to get only real messages in your inbox. Just one mailbox per domain name can be a catch-all one and email forwarding cannot be activated for a catch-all mailbox.