Summary
When a soft bounce indicates 'blocked using Spamhaus' but the IP is not listed, it can be attributed to several factors. Outdated or cached Spamhaus data on the recipient's server, DNSBL propagation delays, and temporary IP listings/delistings are common causes. Shared IP addresses can be impacted by the sending practices of other users. Composite blocking, where Spamhaus considers the overall network reputation, may also be a factor. It's also possible that the bounce message is a false positive or that the recipient's server is misinterpreting the Spamhaus data. Maintaining a good sender reputation by warming up new IPs, regularly checking sender scores, cleaning email lists for spam traps, and adhering to best practices are critical.
Key findings
- Outdated Data: Receiving servers might have cached or outdated Spamhaus data.
- Propagation Delay: DNSBL propagation delays can cause discrepancies.
- Temporary Listings: IPs may be temporarily listed and delisted.
- Shared IP Impact: Shared IPs are vulnerable to actions of other senders.
- Composite Blocking: Spamhaus considers overall network reputation.
- False Positives: Bounce messages might be false positives.
Key considerations
- Check Sender Score: Regularly monitor sender score for insights.
- Clean Email Lists: Remove spam traps and invalid addresses.
- Warm-up IPs: Gradually warm up new IPs to build reputation.
- Multiple Blocklist Checks: Use multiple tools to check blocklists for accuracy.
- Review Sending Practices: Ensure adherence to email sending best practices.
- Investigate Recipient-Side Issues: Contact the recipient to investigate server-side configurations and potential misinterpretations of Spamhaus data.
What email marketers say
9 marketer opinions
When a soft bounce indicates 'blocked using Spamhaus' despite the IP not being listed, several factors could be at play. The recipient's mail server might have cached outdated Spamhaus data, or there could be delays in propagating Spamhaus updates across different systems. Temporary listings, issues with shared IP reputation due to other senders, outdated DNS records on the recipient's side, and false positives are all possibilities. Checking your sender score, looking for spam traps, and warming up new IPs correctly are also crucial considerations.
Key opinions
- Cached Data: Receiving mail servers may use cached, outdated Spamhaus data.
- Propagation Delays: Delays occur in propagating Spamhaus updates across systems.
- Shared IP Issues: Shared IPs can be affected by other senders' activities.
- Outdated DNS: Recipient servers might have outdated DNS records.
- False Positives: The block message might be a false positive.
Key considerations
- Check Sender Score: Regularly monitor your sender score for insights into potential blocking issues.
- Look for Spam Traps: Scrub your email list for spam traps to avoid being flagged.
- Warm-up IPs: Warm up new IPs slowly to establish a good sending reputation.
- Use Multiple Blocklist Tools: Data can vary and take time to update across networks so it is important to check multiple blocklist tools.
- Check Compliance: Always ensure sending practices are compliant with Spamhaus policies.
Marketer view
Email marketer from the forum explains that the recipient's server may be using outdated DNS records. The DNS record of the sender's IP could have been updated, but the recipient's server may still be using an old, outdated record. This can cause the server to incorrectly identify the sender's IP as being blacklisted.
24 Dec 2023 - Email Marketing Forum
Marketer view
Email marketer from Senderok explains that using multiple tools to check blocklists is important because data can vary and take time to update across networks.
3 Feb 2025 - Senderok
What the experts say
3 expert opinions
When receiving a soft bounce notification indicating 'blocked using Spamhaus' despite the IP address not appearing on any Spamhaus lists, several explanations are possible. The IP could have been listed and removed quickly, or if using a shared IP, another sender's actions might be the cause. It could also be a false positive due to misinterpretation of Spamhaus data or a configuration problem at the recipient's end. DNSBL propagation delays could also cause discrepancies between real-time listing status and bounce reports.
Key opinions
- Transient Listing: IP may have been listed and delisted before a manual check.
- Shared IP Influence: Shared IPs are vulnerable to actions of other senders on the same IP.
- False Positive: Bounce message could be a misinterpretation of Spamhaus data.
- Propagation Delay: DNSBL propagation delays might lead to inaccurate reporting in bounce messages.
Key considerations
- Contact Recipient: Suggest the recipient investigates their server configuration and Spamhaus data interpretation.
- Monitor Shared IP: If on a shared IP, monitor the IP reputation and consider moving to a dedicated IP if issues persist.
- Acknowledge Inaccuracy: Be aware that bounce messages might not always reflect the current listing status due to delays.
Expert view
Expert from Spam Resource explains that the bounce message might be a false positive. The recipient's server may be misinterpreting the Spamhaus data, or there could be a configuration issue on their end that's causing the incorrect block. They suggest contacting the recipient to investigate the issue on their side.
27 Feb 2024 - Spam Resource
Expert view
Expert from Email Geeks explains that it's possible the IPs were listed and then removed before the record was checked. Also, if it's a shared IP, it could be completely unrelated to the sender's message and that 99.99% of the time IP based blocking is completely out of their control. If it *is* in the senders control, the result is often removal from the shared IP pool or ESP.
6 Jul 2024 - Email Geeks
What the documentation says
5 technical articles
A soft bounce indicating 'blocked using Spamhaus' when the IP isn't listed can stem from several documented reasons. Spamhaus notes composite blocking and recent listing/delisting as possibilities. Microsoft suggests it could be a temporary block, advising a review of sending practices. Postmark points to outdated DNSBL information on the recipient's server. SparkPost echoes the potential for temporary issues and composite blocking. AWS highlights the importance of building and maintaining a good IP reputation through responsible sending practices, which impacts deliverability and can prevent such blocks.
Key findings
- Composite Blocking: Spamhaus may employ composite blocking, considering overall network reputation, even if a specific IP isn't listed.
- Temporary Listing: IPs can be temporarily listed and delisted, leading to transient blocking notifications.
- Outdated DNSBL: Recipient servers using outdated DNSBL information may incorrectly block messages.
Key considerations
- Review Sending Practices: Assess and optimize sending practices to align with best practices and avoid triggering Spamhaus blocks.
- Check Spamhaus Directly: Visit Spamhaus to understand block reasons and request delisting if appropriate.
- Maintain IP Reputation: Focus on building and maintaining a positive IP reputation through opt-in practices and high-quality content.
- Check DNSBL Information: Be aware that blocks can happen if the recipients have outdated DNSBL
Technical article
Documentation from Spamhaus explains that while an IP might not appear on the Spamhaus Block List (SBL) when queried, it may still be contributing to a block. This could be due to factors like recent listing and delisting, or the use of composite blocking where the overall network reputation is considered.
31 May 2025 - Spamhaus
Technical article
Documentation from Postmark Support explains that a soft bounce related to Spamhaus might occur if the recipient's server is using outdated DNSBL (DNS Block List) information. They suggest that the issue may resolve itself as the recipient's server updates its DNSBL information.
17 Sep 2021 - Postmark
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