From the developer: "This testing tool allows users to scan and check their open relay servers. It tests smtp relays, blind anonymous relays and public proxy lists also. Used by some people at abuse.net and sendmail.org to test open relays. Site Features include : Open Relay Database, Open Relay Usage Articles, FAQs %26 How-tos, Closing Relays and Protecting your Mail Server, Anti Spam Tips, Public SMTP List, Server list updated daily."

Note: While this product allows you to check for open relays on your server, it may also add your server to a list of known open relays that is for sale at OpenRelayCheck.com.