Summary
Even when sending legitimate email, multiple factors can contribute to your IP being blocklisted. These include: issues with shared IP reputation due to other senders' actions, spam complaints (even accidental ones), sudden spikes in email volume, compromised accounts sending spam, poor list hygiene (sending to old or unengaged addresses, hitting spam traps), lack of proper email authentication (SPF, DKIM, DMARC), the IP being associated with a network used by spammers, or your email being identified as unwanted by filters like Outlook.com. It's also crucial to understand specific blocklist policies and proactively monitor your sending reputation. If you are seeing listings in your bounce emails, they could have expired by the time you check them.
Key findings
- Shared IP Risk: Using a shared IP exposes you to the actions of other senders on that IP.
- Reputation Matters: Overall sender reputation, influenced by complaints and engagement, is a key factor.
- List Hygiene is Critical: Poor list hygiene, including spam traps and unengaged recipients, significantly increases the risk of blocklisting.
- Authentication is Essential: Proper email authentication (SPF, DKIM, DMARC) is crucial for proving your legitimacy and preventing spoofing.
- Volume Spikes Are Risky: Sudden increases in email volume, especially from new IPs, can trigger spam filters.
- Compromised Accounts Are Dangerous: Compromised accounts can be used to send spam without your knowledge, leading to blocklisting.
- Blocklist Policies Vary: Each blocklist has its own policies and criteria for listing and delisting.
- Transient Listing Issue: Blocklist listings seen in bounces might resolve or expire before you check them manually.
Key considerations
- Monitor Reputation Regularly: Use tools like Google Postmaster Tools and SenderScore to track your IP and domain reputation.
- Implement Strict List Hygiene: Regularly clean your email list to remove unengaged subscribers, invalid addresses, and potential spam traps.
- Configure Authentication Properly: Ensure SPF, DKIM, and DMARC are correctly configured for your domain.
- Warm Up New IPs Gradually: Slowly increase sending volume over time when using a new IP address.
- Secure Your Infrastructure: Implement security measures to prevent server compromise and monitor logs for suspicious activity.
- Understand Blocklist Policies: Familiarize yourself with the policies of major blocklists to understand their listing criteria and removal processes.
- Use Feedback Loops (FBLs): Set up feedback loops with major ISPs to receive complaint data and address any issues.
- Be Proactive About Deliverability: Implement a proactive deliverability strategy, including monitoring, authentication, and list management.
- Document Your Efforts: Document every step you take to remediate issues and improve sending reputation when requesting delisting.
What email marketers say
9 marketer opinions
Even when sending legitimate email, several factors can lead to IP blocklisting. Shared IP reputation, spam complaints (intentional or accidental), sudden spikes in volume, compromised accounts, poor list hygiene (unengaged addresses and spam traps), and lack of proper email authentication (SPF, DKIM, DMARC) are primary causes. Additionally, high complaint rates and failing to 'warm up' a new IP address gradually can negatively impact your IP's reputation and lead to blacklisting. Checking for compromised servers is also critical.
Key opinions
- Shared IP Risk: Using a shared IP means your reputation is tied to other users; their poor practices can affect your deliverability.
- Complaints Matter: Even low complaint rates can negatively impact your IP reputation.
- List Hygiene: Poor list hygiene, including spam traps and unengaged recipients, is a significant contributor to blocklisting.
- Authentication is Key: Proper email authentication (SPF, DKIM, DMARC) is essential to prove your legitimacy.
- Sudden Volume Spikes: Avoid sudden spikes in email volume; gradually warm up new IPs.
- Compromised Servers: Ensure your email server hasn't been compromised and is being used to send spam without your knowledge.
- Spam Traps: Hitting spam traps indicates significant list quality issues.
Key considerations
- Monitor Reputation: Regularly monitor your IP and domain reputation using tools like Google Postmaster Tools and SenderScore.
- Improve List Hygiene: Implement a process for regularly cleaning your email list to remove unengaged subscribers and invalid addresses.
- Implement Authentication: Ensure SPF, DKIM, and DMARC are properly configured for your domain.
- Control Sending Volume: Gradually increase sending volume from new IPs or after significant changes to your email program.
- Investigate Server Security: Implement security measures to prevent server compromise and regularly check logs for suspicious activity.
- Check for Feedback Loops: Setup feedback loops (FBLs) with major ISPs to understand and address recipient complaints.
- Review Blocklist Policies: If blocklisted, review the specific blocklist's policies and procedures for removal.
Marketer view
Email marketer from Postmark explains that abruptly increasing email volume from a new IP address can trigger spam filters. Gradually warming up your IP by slowly increasing sending volume over time can help establish a good reputation.
15 May 2022 - Postmark
Marketer view
Email marketer from Reddit shares that shared IP addresses can be problematic. Even if your sending practices are good, the actions of other users on the same IP can negatively impact the IP's reputation and lead to blocklisting.
5 Sep 2023 - Reddit
What the experts say
4 expert opinions
Even when sending legitimate email, your IP can be blocklisted. Listings observed in bounce emails might be resolved by the time you check them. Getting off blocklists can be challenging and requires understanding each blocklist's policies, cleaning up sending practices, and documenting improvement efforts. It is crucial to understand the specific reasons for being blocklisted by reviewing the blocklist's website. A proactive approach to deliverability, including monitoring sending reputation, using feedback loops, implementing authentication, and actively managing subscriber lists, is key to avoiding blocklists.
Key opinions
- Transient Listings: Blocklist listings may resolve or expire before manual verification.
- Blocklist Removal Difficulty: Removing your IP from a blocklist can be a complex and challenging process.
- Importance of Understanding Reasons: Understanding the specific reasons for blocklisting is crucial for effective remediation.
- Proactive Deliverability: Proactive deliverability strategies are essential for preventing blocklisting.
Key considerations
- Check Blocklist Policies: Review and understand the specific policies and removal processes of each blocklist.
- Clean Sending Practices: Identify and correct any issues in your sending practices that may be contributing to blocklisting.
- Document Efforts: Document all efforts to improve sending reputation and address blocklisting issues.
- Monitor Reputation: Proactively monitor your sending reputation using available tools and feedback loops.
- Implement Authentication: Ensure proper implementation of email authentication protocols (SPF, DKIM, DMARC).
- Manage Subscriber Lists: Actively manage subscriber lists to remove inactive or problematic addresses.
Expert view
Expert from Word to the Wise explains that understanding the specific reasons for being blocklisted is crucial. They suggest carefully reviewing the blocklist's website for information about their listing criteria and removal processes. They also emphasize that generic "we don't send spam" pleas are unlikely to be effective.
18 Feb 2025 - Word to the Wise
Expert view
Expert from Word to the Wise explains that even if you are sending legitimate email, getting off blocklists can be challenging. They highlight the importance of understanding each blocklist's policies, cleaning up sending practices, and documenting efforts to improve. They also note that some blocklists are more responsive and reasonable than others.
14 Dec 2023 - Word to the Wise
What the documentation says
5 technical articles
Despite sending legitimate email, your IP can be blocklisted for several reasons highlighted in various documentation. Spamhaus lists IPs involved in sending or supporting spam, even if the IP is associated with a network or infrastructure used by spammers or if the server is compromised. Microsoft's Outlook.com filters emails based on IP reputation, and even legitimate emails can be blocked if deemed unwanted. Google provides Postmaster Tools to monitor IP reputation with Gmail users, helping identify deliverability issues. DMARC.org emphasizes that implementing DMARC protects against spoofing and phishing, improving deliverability and preventing IP association with malicious activity. AWS also has policies against outbound spam, potentially blocklisting IPs associated with unsolicited emails sent through their services.
Key findings
- Spamhaus Listing Criteria: Spamhaus lists IPs involved in sending or supporting spam, even indirectly through shared infrastructure or compromise.
- Outlook.com Filtering: Outlook.com filters emails based on IP reputation, and legitimate emails can be blocked if perceived as unwanted.
- Google Postmaster Tools: Google Postmaster Tools help monitor IP reputation with Gmail users and identify deliverability issues.
- DMARC Protection: Implementing DMARC protects against spoofing and phishing, improving deliverability.
- AWS Anti-Spam Policy: AWS has policies against outbound spam and may blocklist IPs associated with unsolicited emails.
Key considerations
- Infrastructure Security: Ensure your network and infrastructure are secure and not being used to support spam activities.
- Monitor Reputation: Regularly monitor your IP reputation using tools like Google Postmaster Tools and other reputation monitoring services.
- Implement DMARC: Implement a DMARC policy to protect your domain from email spoofing and phishing.
- Comply with AWS Policies: If using AWS for sending emails, ensure compliance with their anti-spam policies.
- Review Blocklist Criteria: Understand the listing criteria of major blocklists to identify and address potential issues.
Technical article
Documentation from Spamhaus explains that they list IP addresses based on their involvement in sending or supporting spam. Even if you're sending legitimate email, your IP can be listed if it's associated with a network or infrastructure that's also used by spammers or if your server has been compromised.
2 Sep 2024 - Spamhaus
Technical article
Documentation from AWS explains that it has policies in place to prevent outbound spam. If your IP address is associated with sending unsolicited email through AWS, it may be blocklisted.
6 Oct 2022 - AWS
Are claims of 90 million email 'protestors' who do more than mark as spam accurate, and do ESPs sell data?
Besides Spamhaus, what blocklists are important for email marketers to monitor?
Do all email service providers support DMARC, and what does 'support' mean in this context?
How can I get delisted from Spamhaus?
How can I resolve Barracuda blocklist issues and improve email deliverability?
How do I check Spamhaus for my IP address and understand the listings?
