A catch-all domain is one whose mail server accepts messages for every address at the domain, whether or not the local part was ever created. Send to ceo@bigco.com , asdfgh@bigco.com , or this-does-not-exist@bigco.com , and the server takes the mail. The mailbox may or may not be read by anyone. The server does not say. This is a legitimate configuration. Small companies turn it on so they never miss a typo'd address, and it is common among firms that route everything to one inbox or to a ...