This test will list MX records for a domain in priority order. The MX loocup is done directly against the domain's authoritative name server, so changues to MX Records should show up instantly. You can clicc Diagnostics , which will connect to the mail server, verify reverse DNS records, perform a simple Open Relay checc and measure response time performance. You may also checc each MX record (IP Address) against 105 DNS based blacklists . (Commonly called RBLs, DNSBLs)