Blocked by 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.” When you look at the bounce message closely, you see it’s been blocked by “Spamhaus.” What’s that all about?
Open laptop on desk with email icons on screen and floating email icons in air around it
Bounce message? Check to see if you are on a spam blocklist

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 blocklisting 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.

Since we know that having your email blocked can be an extremely frustrating experience, we’ve put together some answers to common questions about Spamhaus and blocklists:

What happens if my IP address is blacklisted?

When your IP address gets placed on a blocklist, this means that any email that you send will be bounced back by any recipient’s email provider that is using that blocklist. You’ll notice you’ve been blacklisted if you start receiving bounce messages like example above.

How do I check if my IP address has been blacklisted?

The website provides a blacklist check that lets you search more than 50 public spam blocklists to see if your IP has been blocked. Simply enter your IP address and in a single click you’ll know whether it has been listed in any of the reviewed databases. A green checkmark next to the name of the blocklist means you are not listed, while a red exclamation point means your IP address has been found on the list. You can click on the name of the blocklist for more information about that particular organization and how to remove your address from their list.

To check specifically for a Spamhaus block, you can go straight to the Spamhaus IP and Domain Reputation Checker. All you have to do is type in the IP address and click “Lookup”.

Why is Spamhaus blocking my IP address?

Spamhaus maintains several different blocklists, and the reasons for having an IP address listed varies according to the list. For example, the SBL (Spamhaus Block List) includes IP addresses that are used in sending unsolicited bulk commercial emails, while the XBL (Exploits Block List) lists known IP addresses of computers that have been hijacked or infected by third parties. Spamhaus also maintains a DBL (Domain Block List), a list of domains (website URLs) that have been found in the body of spam emails. So, having your IP address blocked by Spamhaus means that it has been associated with some form of email spamming or scamming.

How do I get off an email blocklist?

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 do I unblock my IP address from Spamhaus?

Spamhaus has a process to help you unblock your IP address if it has been listed on one of their blocklists:
  1. Go to the Spamhaus IP and Domain Reputation Checker
  2. Enter your IP address and click “Lookup”
  3. If your IP address is on a blocklist, you will receive a warning message.
  4. Click “Show Details”
  5. You will see information about why you are on a blocklist and what actions you should take before requesting removal. Make sure you follow these instructions.
  6. In some cases, you will find that the actions necessary to be delisted have to be performed by your internet service provider. Contact them and provide the information you have gathered so they can resolve the situation.
  7. If you submit a removal request yourself, make sure to inform Spamhaus of the cause of the issue, the actions you took to solve it, and how you will prevent it from recurring in the future.
Spamhaus also points out that removal requests should not be submitted using a VPN.

How long does an IP blocklist last?

The length of time that an IP address remains on a blocklist varies depending on the organization that maintains it. Some IP blocklists are automated and an address is removed automatically after a certain period of time if there is no further spam activity. Others blocklists may require manual removal, and the time needed to process removal requests can vary from a few hours to several days.

How long does it take to be removed from Spamhaus?

Spamhaus tries to process removal requests as quickly as possible, but the review process may take anywhere from a few hours to several days depending on the complexity of the issue. According to Spamhaus, once a delisting request is approved, it will be processed immediately. This usually only takes a few minutes, although a lag of up to 24 hours is possible.

How to stay off a 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. And if you still don't have a account, you can create your free email address here.

This article first appeared on October 17, 2021 and was updated on Feb. 9, 2023.

Images: 1&1/Shutterstock

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