IP and Domain Reputation Checker
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Your email has bounced back from the recipient

If you are viewing this page, you have likely sent an email that was not delivered to the recipient. In the resulting bounced email message you have found and clicked this link: https://www.spamhaus.org/returnc/pub/2400:cb00:376:1024::ac46:547a

The problem doesn’t relate to your email set-up.

Why has my email not been delivered?

  • The problem is with the recipient’s email server configuration.
  • This is not due to an issue with your email set-up.
  • It is not because you are listed on one of our blocklists.

What do I need to do next?

If the email is urgent or essential:

  • Call the recipient and tell them that they have an issue with receiving emails.
  • Ask the recipient to urgently contact their email server administrator. This page provides the information required to correct this issue: Using our public mirrors? Check your return codes now.

For non-urgent emails

  • Try and resend the email in 24 hours, allowing the recipient’s email administrators time to resolve the problem.

Want more technical detail?

We’ve provided the above information for the everyday email user; however, if you’re technically minded and want to learn more, keep reading…

Queries cannot successfully be made to the Spamhaus free infrastructure via public/open resolvers. This is to protect the infrastructure from abuse by large-volume queriers. If you’d like to take a deeper dive into this, check out successfully accessing Spamhaus’ free blocklists using a public DNS.

Some users continue to query Spamhaus blocklists via public resolvers, unaware that this means that our data does not actually protect their mail stream. We have introduced an error code for these users to provide a clear signal that there is an issue, and that the mailserver configuration needs to be updated.

A free upgrade: Spamhaus DQS

To succesfully query Spamhaus via public/open resolvers, there is a FREE service which delivers the intelligence faster and with additional blocklists available to increase catch-rates: Spamhaus Data Query Service.

Here are the details of how to make the change:

Alternatively, if you’d like to continue using the free public infrastructure, please ensure that your queries come from a dedicated IP with attributable reverse and forward DNS. Here is information on how to correctly configure commonly used MTAs for use with the public mirrors.