Is there no auth being used on the email server?
Sep 5 13:08:05 mail send: 1409915285.649222 delivery 4: success: User_and_password_not_set,_continuing_without_authentication./<testuser@gmail.com>_173.194.66.26_accepted_message./Remote_host_said:_250_2.0.0_OK_1409915285_p3si1616229wjy.51_-_gsmtp/
