Spamhaus, bounced emails and blocked IP addresses

Your email bounces back with a permanent error “A message that you sent could not be delivered to one or more of its recipients.”
Open laptop on desk with email icons on screen and floating email icons in air around it
Check the bounce message to see if you are on an spam blocklist
When you look in at the bounce message closely, you see it’s been blocked by “Spamhaus.” What’s that all about?

Spamhaus and other spam databases

 Oftentimes the error message will contain a reference to an organization such as Spamhaus, SpamCop or a similar anti-spam group. For example:
SMTP error from remote server for RCPT TO command, host: (876.00.1.16) reason: 550 5.7.1 Service unavailable, Client host [] blocked using Spamhaus. To request removal from this list see
Organizations like The Spamhaus Project track email spammers and spam-related activity by compiling blocklists (also called “blacklists”) of IP addresses, domain names, and email addresses that are associated with spamming. These blocklists are then used by internet service providers and email servers with the aim of cutting down the amount of spam that arrives in their customers’ inboxes.
If you send an email and your recipient or their mail system works with Spamhaus, SpamCop, or another blacklisting organization, it means that your message may be refused as suspected spam if it is sent from an IP address that is on the blocklist.

How to get off an email blacklist

Don’t worry – if you are not actually sending spam and have been mistakenly blacklisted, there are steps you can take to resolve the issue. The best way to solve this problem is by contacting your internet service provider (ISP) and requesting the de-listing of the IP address. If the bounce message lists the specific organization responsible for the block, as in the example above, you can also visit its website for more information: Spamhaus, SpamCop, etc. all have processes in place to help with blocklist removal.

How to stay off the spam blocklist

If you are having repeated issues with your emails bouncing, there are a few steps you can take to avoid them being mistakenly identified as spam:
  1. Keep your email account from being hijacked by spammers: Maintain a strong password, scan your computer for malware, and consider activating 2FA.
  2. If you send out emails to a mailing list, make sure to give recipients a way to opt-out: If too many people mark your mail as spam, your email address could be blacklisted. You should also regularly remove inactive email addresses from the list.
  3. Ask your recipients to add to you their list of trusted senders, usually called a “whitelist” or “allowlist.”
Good to know: If you are a customer and have followed all the steps above, but the issue of emails bouncing back persists, we can investigate further. Please contact us and provide us with a recent bounce message and the body of the email you tried to send, and we will try to determine why the email was detected as spam.

If you are experiencing issues with bounced emails, we hope this post will help you resolve them. We look forward to your feedback below!

Images: 1&1/Shutterstock

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