The California organization consists of volunteers who are tired of the unwanted junk filling up their mailboxes. MAPS also sends an email to the email administrator notifying him that his site has been listed and includes instructions on how to respond. Blacklisting is apparently very effective. As an email administrator, you might wonder why you should bother closing Third-Party Mail Relay. It hasn't affected your network and you are already behind schedule on other projects.
Relays can cause a denial of service .
When someone is using your resources without your permission they are stealing from you. Recovering from this type of attack can be very expensive . Think of the time and energy required in order to recover from a crash. You will have to spend countless unplanned hours getting your email server back on line. You will also have to explain to your users and management why their email was unavailable.