How does Spamhaus block spam emails?

My IP is on a blacklist. What to do?

If e-mails do not reach certain recipients, it is possible that your IP address has been blacklisted. In most cases you will then receive a corresponding error message from the receiving mail server. This can be, for example:

  • Remote host said: 554 Transaction Failed Spam Message not queued.
  • Client host [203.0.113.42] blocked using (anything) .spamhaus.org; http://www.spamhaus.org/query/bl?ip=203.0.113.42

This message states that the recipient has identified your email as spam and that it has been blocked.

Then check whether your public IP address (which you also use to send e-mails) is on one of the known blacklists. There are numerous websites that allow blacklist queries. E.g. http://www.mxtoolbox.com/blacklists.aspx.

If your IP address is on one or more lists, this can have various causes:

If you do not have a static IP address, it is possible that the person who had the IP address before you sent it spam. In this case, it should be sufficient to simply restart your router or unplug it and plug it in again. Then you should get a new IP address. Then try to send the email again.

If you have a fixed IP address, you must first find the cause of the listing. For example, it can be one of the following:

  • You have recently sent a lot of emails to numerous invalid recipients, e.g. in the form of a newsletter.
  • There is a virus or trojan on one of your PCs that is sending uncontrolled spam.

After you've found the cause and fixed it, most blacklists allow you to request deletion of your IP address. To do this, visit the website of the corresponding blacklist.

Important: Only apply for deletion after you are sure that you have found the cause and eliminated it. If you continue to send spam after the deletion request, you may be blocked for a long time.