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How to Test URI DNS Blocklist Filter

Author: Dennis Chege Updated

Overview

This article outlines the process that should be followed to test whether the URI DNS Blocklist Anti-Spam filter is properly configured and filtering spam as expected.

Prerequisites

Testing URI DNS Blocklist functionality is done by sending an inbound test email that is purposely composed in such a way that it will be blocked by the filter.

For this purpose, you will require:

  • An SMTP client (such as KMail or Microsoft Outlook) connected to your SMTP server or Exchange environment.
  • Administrative access to a local DNS server for the creation of the test DNS records.
  • MailEssentials configured to use this local DNS for name resolution.

Solution

Follow the below procedure to test the URI DNS Blocklist Anti-Spam filter.

Note: The steps assume that you are using the local DNS server that is part of the Windows Server operating system. The same steps will apply for any other DNS service that you have administrative access to.

  1. Open the local DNS server configuration

  2. Create a subdomain surbl (surbl.gfime.local) under your primary local domain (gfime.local)

  3. Create an A record inside surbl.gfime.local for some URI (e.g. spammer.com, IP 1.2.3.4)

    A_record_inside_surbl.gfime.local.png

  4. Run nslookup to confirm that the name resolution works

    Test_A_record.png

  5. Add surbl.gfime.local to the URI DNS Blocklist

    Adding_surbl.gfime.local_to_dns.png

  6. Using KMail or another suitable SMTP client, send an email containing spammer.com in the email body.

    KMail_Spammer_Test.png

Confirmation

  1. Navigate to GFI MailEssentials > Dashboard and open the Logs tab. Locate the test email you sent which should be blocked with a Scan Result of Blocked [URI DNS] as shown below:

    URI_DNS_Blocklist_Success.png

    • Note: If the Scan Result shows a different Anti-Spam filter, this means URI DNS Blocklist was configured with a lower priority and you may temporarily disable that filter or alternatively adjust the priority by going to GFI MailEssentials > Anti-Spam > Filter Priority 
  2. Further information can be obtained by checking the debug logs as described in How to determine why the URI DNS Blocklist spam filter blocked or allowed a message.

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