How to use the Blocklist Tester


  • Go to the home page, enter the email address for the server you want to test, and click “Access Portal”.
  • The BLT will execute an MX Probe test. The probe sends the following SMTP commands but does not deliver an email: EHLO, MAIL FROM, RCPT TO, QUIT.
  • If the MX Probe can confirm that the host is responsive and accepting messages for the email address, the outcome is “good”, and we send a verification email to your registered email address.
  • The verification email contains a link to log in. You can use this link to access the portal as many times as you want.
  • If you aren’t receiving a verification email, we provide some diagnostics of the MX Probe test we’ve performed. To view these, click “View delivery details.”


  • Once you’ve accessed the test page, you can run tests on either the Data Query Service or the Public Mirrors.
  • Select which of the following tests you would like to complete: SMTP test emails, Content test emails, or both, and click on “Run Test.”
  • The DNS mail exchanger (MX) records identify the servers which accept mail for a domain. The BLT finds all MX hosts for the email address and repeats the same test sequence for each one.


  • The “Blocklist test report” will take some time to complete. However, you can see each test email result update in real time.
  • Where you want further detail on a result, click on the icon, and this will take you to the “Test email” page, which outlines the SMTP exchange for that particular test.