A third-party mail relay, also called an open relay mail message, is an e-mail message sent through a mail server where neither the sender nor the recipient is a local user. In the past, third-party mail relays were useful for allowing network administrators to debug mail connectivity issues and route mail around known problems. Spammers, however, have learned that by hijacking these open relays, they can in effect "launder" their spam by successfully delivering their unsolicited e-mail while spoofing their own identity.