Add a router before or instead of the dnslookup router: gmail_route: driver = manualroute transport = gmail_relay route_list = * smtp.gmail.com Add a transport: gmail_relay: driver = smtp port = 587 hosts_require_auth = <; $host_address hosts_require_tls = <; $host_address Add an authenticator (replacing myaccount@gmail.com and mypassword with your own account details): gmail_login: driver = plain