If you query the legacy DNSBLs via Cloudflare's DNS move to Spamhaus Technology's free Data Query Service

Are you currently using the Spamhaus Project’s DNS Blocklists (DNSBLs)? Do you access them via the Public Mirrors, for example, query “sbl.spamhaus.org”? Do you use Cloudflare’s DNS? If you’ve answered “yes” to all three of those questions, you need to make some changes to your email infrastructure.

These changes are quick and easy to make, but if you fail to make them, you could find that at some point in 2022, all or none of your email is blocked!

The headlines for those in a hurry

The Spamhaus Project’s Terms of Use state that it doesn’t allow users to query via DNS resolvers where there is no attributable reverse DNS; this includes Cloudflare (we’ll explain why later in this article).

To provide a clear signal to these users that these blocklists are not protecting their email, Spamhaus will return an error code; 127.255.255.254. If you haven’t set up your email servers to accept this error code, all emails could be rejected and bounced back to their sender.

To prevent any issues with your email stream, stop accessing Spamhaus’ free blocklists via the Public Mirrors and start accessing the blocklists via our free Data Query Service (DQS), which you can sign up for here.

Once you’ve verified your email address, you will get access to a “DQS key” to include in your configuration. These config changes take only minutes; see our technical docs for more detail.

Why isn’t the Spamhaus Project allowing Cloudflare users to query its public blocklists?

The blocklists that the Spamhaus Project makes freely available via its Public Mirrors are for small-scale, non-commercial use. To ensure these users have a good quality of service, usage is monitored and measured against the Project’s Terms of Use.

Cloudflare masks organizations’ queries to the Project’s Public Mirrors, so the team can’t attribute usage to individual entities. They have no way of establishing the number of queries a single organization is making.

To provide transparency, these free blocklists can be accessed via the free DQS.

How is the free DQS different from the free Public Mirrors?

• Usage transparency – users register to access the free DQS and are provided with a key that records query volumes.
• Increased performance – blocklists are updated in real time.
• Additional protection – access to more blocklists, including Zero Reputation Domain Blocklist, Domain Blocklist with Hostnames, and Auth Blocklist.

How to access the free DQS

1. Sign up for an account
2. Verify your email address
3. Log in to your account and access your DQS key
4. Update your email configuration. We have config guides for mainstream MTAs.

How will Cloudflare users be prevented from querying Spamhaus’ free DNSBLs?

To ensure its Terms of Use are adhered to, the Spamhaus Project will block queries from a specific IP address outside the policy. It also returns an error code. In the case of querying via an open/public resolver, i.e., Cloudflare, the error code is 127.255.255.254.

If your MTA can’t correctly parse these error codes, serious issues can occur, including bouncing all emails back to their senders and your emails not being queried against the blocklists. Here’s how to properly configure your MTA to process these error codes, if you continue to use the Spamhaus Project’s DNSBLs.

When will the Spamhaus error code for Cloudflare DNSBL users be introduced?

This year, the Spamhaus Project will slowly implement the error code across Cloudflare IP space, commencing from Tuesday, February 15th, 2022.

Please don’t delay – take action now and move to the free DQS.

What if I don’t want to use the free DQS?

1. Use DNS resolvers with attributable DNS to continue being protected by Spamhaus’s IP and domain reputation.
2. If you no longer wish for your mail stream to be protected for free by Spamhaus’ blocklists, remove all associated configurations from your email infrastructure.

Further details

Additional information for Spamhaus Project’s DNSBLs users having issues due to error codes is detailed here.

Previous communications that were sent in relation to these changes can be found here:

• Spamhaus DNSBL return codes: technical update
• Using our public mirrors? Check your return codes now.

Any questions?

Not a problem – reach out to us via Twitter @spamhaustech or our contact form, and we’ll try and answer any question you have or failing that we’ll pass it onto the Spamhaus Project for a response.