Why is Google Postmaster Tools reporting IPs not associated with my domain?
Matthew Whittaker
Co-founder & CTO, Suped
Published 16 Apr 2025
Updated 17 Aug 2025
7 min read
Discovering unfamiliar IP addresses in your Google Postmaster Tools dashboard can be a confusing and concerning experience. You might be seeing IPs that don't belong to your infrastructure, or perhaps from providers like Linode or OVH, which you don't directly use. This situation often leads to questions about how Google associates these IPs with your domain, especially if your own email authentication (SPF, DKIM, DMARC) seems to be in order.
I've seen this issue arise for many businesses, even those with seemingly perfect DMARC compliance. It's a critical issue because it can significantly impact your deliverability, leading to your legitimate emails landing in the spam folder. Understanding how Google identifies and reports these IPs is the first step to diagnosing and resolving the problem.
How Google Postmaster Tools tracks email sending
Google Postmaster Tools provides crucial insights into your email performance with Gmail. It tracks key metrics like spam rate, domain reputation, and IP reputation. The goal is to help senders understand how Google perceives their email traffic and to identify potential issues affecting deliverability. You can gain more insight into these metrics on the Postmaster Tools dashboards.
Gmail primarily associates incoming emails with a specific domain through authentication protocols like SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). SPF allows domain owners to specify which IP addresses are authorized to send email on their behalf, while DKIM adds a digital signature to outgoing emails, verifying that the message hasn't been tampered with and that it originates from the claimed domain. DMARC then ties these two together, providing instructions on how to handle emails that fail authentication.
However, even if an IP address isn't explicitly listed in your SPF record, Google might still attribute mail to your domain if the DKIM signature aligns with your domain, or if your domain appears in the RFC 5321.From header. This can happen legitimately through forwarding services or email service providers, or maliciously through various forms of domain spoofing. It's important to differentiate between these scenarios to effectively troubleshoot, especially if you're experiencing email deliverability issues, like emails going to spam.
Decoding the unexpected IP addresses
The appearance of unassociated IP addresses in your Google Postmaster Tools report can stem from several issues, ranging from benign forwarding to malicious spoofing. It's crucial to identify the root cause to take appropriate action. One common scenario involves bad actors forging your domain, making it appear as though emails are originating from your legitimate sending infrastructure.
Mail from external sources
Unauthorized senders or spammers might forge your domain (especially the RFC 5321.From header) to send emails. Even if these emails fail SPF or DKIM alignment, Google Postmaster Tools may still report the sending IPs, particularly if a volume of mail is seen from those IPs purporting to be from your domain. You should always look for specific non-compliant sources in your DMARC reports, even if your overall compliance rate looks high. This is a sign of email spoofing.
Forwarding or misconfigurations
Sometimes, legitimate emails are forwarded through third-party services that may use their own IPs but maintain your DKIM signature. This can cause their IPs to appear in your Postmaster Tools. Also, if you use multiple email sending services (marketing, transactional, corporate) and some are not properly configured with SPF or DKIM, their IPs could be reported as not directly associated with your domain.
When you observe IPs from cloud providers like linodeusercontent.com or OVH, it's a significant red flag. These are often used by bad actors due to their low cost and ease of setup. While legitimate businesses might use them, their association with your domain, especially with a sudden drop in reputation, strongly suggests unauthorized activity or widespread spoofing attempts, which can also get your domain on a blocklist or blacklist.
It's important to understand that Google's reporting isn't solely dependent on your SPF record. If your domain's DKIM signature is present and valid, Google may attribute the mail to your domain even if the IP address isn't listed in your SPF. This means that a third party might be replaying or forging DKIM signatures to send emails appearing to be from you, a form of authentication theft. Your Postmaster Tools report reflects all traffic Google associates with your domain, regardless of its explicit authorization in your DNS records.
Investigating unassociated IPs in your DMARC reports
When you see unassociated IPs, your DMARC aggregate reports are the most critical tool for investigation. Even if your overall DMARC compliance appears high, dig deeper. Look for specific sources that are failing SPF or DKIM, or sending DMARC-compliant mail from unexpected IPs.
Key DMARC report analysis points
Review sources: Carefully examine all sending IPs and their corresponding domains, especially those not explicitly listed in your SPF or DKIM records.
Examine non-compliant traffic: Pay close attention to emails failing SPF or DKIM. These are often indicators of unauthorized use.
Check aggregate reports: Analyze trends over time to spot anomalies or sudden spikes in traffic from unknown IPs. This can alert you to new spoofing campaigns.
Look for SPF failures: Even if DKIM passes, SPF failures from unknown IPs are red flags. This might indicate that your domain is being used in the MAIL FROM (RFC 5321.MailFrom) address by unauthorized senders.
Subdomain spoofing is another common vector for attackers. If your DMARC policy doesn't explicitly cover subdomains (e.g., using sp=none or sp=quarantine instead of sp=reject for stricter enforcement), attackers can send emails from non-existent subdomains that might still be attributed to your primary domain by Google.
Keep an eye out for IPs associated with anti-spam filters or security services like inkyphishfence.com or cloudfilter.net in your DMARC reports. These are often legitimate, but their presence might indicate that some of your emails are passing through these services before reaching the recipient's inbox, which can sometimes impact how IPs are reported in Postmaster Tools.
Actions to take and long-term prevention
If you suspect unauthorized sending, the most effective long-term solution is to move your DMARC policy to enforcement (p=quarantine or p=reject). This instructs receiving mail servers, including Gmail, to quarantine or reject emails that fail DMARC authentication and are sent from unauthorized IPs. This is crucial for safeguarding your domain's reputation and preventing bad actors from exploiting it. For more detailed guidance, consider reviewing the simple guide to DMARC, SPF, and DKIM.
Problem
Solution
Unauthorized sending/spoofing
Implement a stricter DMARC policy (p=quarantine/reject) to prevent unauthorized use.
Shared IP reputation issues
Consider dedicated IPs or a more reputable sending service if shared IPs are causing problems.
Misconfigured services
Verify SPF and DKIM records for all authorized sending sources. Use a deliverability tester.
Regularly monitoring your Google Postmaster Tools and DMARC reports is key to maintaining good sender reputation. This proactive approach helps you quickly identify and address anomalies, such as unexpected IP addresses or sudden drops in reputation. Don't solely rely on overall compliance metrics; delve into the specifics of your reports to catch subtle signs of trouble.
Finally, ensure that all legitimate sending sources are properly authenticated with SPF and DKIM and accounted for in your DMARC setup. This includes transactional email services, marketing platforms, and any other third-party tools that send email on your behalf. A robust authentication setup is the best defense against unauthorized use and ensures your email reaches the inbox.
Summary and next steps
Seeing unassociated IPs in your Google Postmaster Tools can be perplexing, but it typically points to either unauthorized use of your domain (spoofing) or complex, legitimate forwarding scenarios. The key to resolving this lies in thorough analysis of your DMARC reports, understanding how Google attributes mail, and maintaining robust email authentication practices.
By actively monitoring your email ecosystem, implementing strong DMARC policies, and ensuring all your legitimate sending sources are correctly authenticated, you can protect your domain's reputation, prevent unauthorized senders from impacting your deliverability, and ensure your emails consistently reach their intended recipients' inboxes.
Views from the trenches
Best practices
Actively monitor DMARC aggregate reports to identify all sending sources, authorized and unauthorized.
Ensure all legitimate third-party senders are properly configured with SPF and DKIM for your domain.
Gradually move your DMARC policy to quarantine or reject to protect your domain from spoofing.
Regularly check Google Postmaster Tools for any unexpected changes in IP or domain reputation.
Assuming Google Postmaster Tools only reports IPs explicitly in your SPF record.
Not considering email forwarding services or obscure legitimate senders.
Panicking over bad IP reputation for unassociated IPs without checking domain reputation.
Expert tips
If your domain reputation is good, focus on strengthening DMARC rather than obsessing over unknown IPs.
Look for authentication theft like DKIM replay if SPF and DKIM reports seem clean.
Review your DMARC policy's subdomain handling (sp tag) to ensure comprehensive coverage.
Be aware that Google Postmaster Tools can sometimes be overly broad in its IP reporting.
Expert view
Expert from Email Geeks says Linode and OVH are low-cost VPS providers known to be utilized by many bad actors, which suggests a high likelihood of unauthorized use if such IPs are appearing.
February 1, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks says if Google Postmaster Tools shows IPs but DMARC reports for those IPs are missing, there might be an issue with the DMARC setup, possibly concerning subdomain coverage.
