Overview
GWEEP Relays tracks servers that allow unauthorized mail relaying. Mail relaying itself is a normal email delivery mechanism, but "open" relays β servers that let anyone forward email without authentication β are key spam infrastructure.
How It Works
GWEEP tests SMTP servers for relay behavior by attempting to send third-party email through them. If the server accepts and forwards these messages, it indicates an open relay problem and the IP gets listed.
How to Get Delisted
Fix your mail server to only relay for authorized users and internal domains. In Postfix, check smtpd_relay_restrictions. In Exchange, review receive connector permissions.