Summary
Unexpected IP addresses appearing on Senderscore for a dedicated IP can be a puzzling issue, especially when you are certain your sending is consolidated through a single email service provider. While it might seem alarming, this phenomenon is often innocuous and can typically be attributed to factors outside of direct sending activity, primarily email forwarding by recipients. Understanding these underlying causes is key to accurately interpreting your sender reputation data and preventing unnecessary concern about your email deliverability.
Key findings
- Email forwarding: The most common reason for unexpected IPs appearing on Senderscore (or similar reputation metrics) for dedicated IPs is email forwarding. When a recipient forwards your email, their mail server might re-transmit it, causing the message to be associated with an IP address that is not your original sending IP. Senderscore may then pick up this intermediate IP.
- Data aggregation: Senderscore aggregates data from various sources to provide a comprehensive view of an IP's sending reputation. This aggregation can sometimes include IPs involved in re-routing or forwarding, leading to the appearance of secondary IPs linked to your domain.
- Innocuous activity: In most cases, especially if your brand is not a likely target for phishing or spoofing, the appearance of these IPs is harmless. It merely reflects how emails traverse the internet through various mail servers and ISPs.
- DMARC reports: Your DMARC reports provide valuable insight into all mail streams claiming to be from your domain. These reports can help confirm if the unexpected IPs are indeed related to legitimate email forwarding or other authorized services, rather than malicious activity.
Key considerations
- Verify DMARC setup: Ensure your DMARC records are properly configured and your policy is set to audit or enforce. This will give you visibility into all email streams that are attempting to send on behalf of your domain.
- Analyze DMARC reports: Regularly review your DMARC aggregate reports for any IPs that are failing authentication (SPF or DKIM) while sending on your behalf. If the unexpected IP shows up here with authentication failures, it reinforces the forwarding scenario.
- Contextual analysis: Consider the owner of the unexpected IP. If it belongs to a major Internet Service Provider (ISP), it is highly likely to be related to email forwarding. A quick search of the IP can often reveal its owner.
- Overall reputation: Focus on your overall sender reputation and deliverability rates. A single unexpected IP on Senderscore that isn't causing measurable deliverability issues or triggering DMARC alerts is usually not a cause for alarm. For more insights into how IP reputation is influenced, refer to LuxSci's guide on IP reputation factors.
What email marketers say
Email marketers frequently encounter situations where unexpected IP addresses appear on their Senderscore, even when using dedicated IPs. Their collective experience suggests that this is a relatively common occurrence, often not indicative of a serious underlying problem. Marketers highlight the importance of understanding how email forwarding can obscure the true origin of an email in reputation reports.
Key opinions
- Common occurrence: Many marketers report seeing unexpected IPs on their Senderscore, suggesting it's not an isolated incident but rather a regular part of email ecosystem dynamics.
- Forwarding is primary suspect: Email forwarding is consistently cited as the most probable cause. When recipients forward emails, the message often gets routed through other mail servers, whose IPs might then register on reputation tools like Senderscore.
- Often harmless: For the most part, marketers consider these rogue IP appearances to be harmless, particularly if there are no signs of actual deliverability issues or malicious activity.
- Dedicated IP nuances: While dedicated IPs are meant to provide sole control over reputation, the complex routing of emails can still introduce other IPs into the reputation assessment.
Key considerations
- DMARC reports for verification: Marketers advise leveraging DMARC reporting to gain additional reassurance. DMARC reports show all IPs sending mail on behalf of your domain, including those that might fail SPF checks due to forwarding.
- Focus on overall deliverability: Instead of fixating on a single unexpected IP, marketers suggest focusing on broader deliverability metrics and overall sender reputation.
- IP warming relevance: The appearance of unexpected IPs can be more concerning for new dedicated IPs that are still undergoing IP warming, as their reputation is still fragile.
- Don't panic: The consensus among marketers is to avoid immediate alarm. These instances are frequently benign and do not indicate a compromise or a major problem with the sender's own infrastructure. Learn more about why IPs get flagged as spam.
Marketer view
An email marketer from Email Geeks observes unexpected IP addresses appearing on Senderscore for their dedicated IP, despite only using one ESP, and seeks advice on interpreting this sudden change.
Marketer view
An email marketer from Email Geeks confirms that unexpected IP appearances on Senderscore are a common occurrence.
What the experts say
Deliverability experts largely concur that unexpected IP addresses appearing on Senderscore for dedicated IPs are often a result of recipient-side activities, such as email forwarding. They emphasize that while this can be alarming, it typically doesn't signify a direct compromise of the sender's infrastructure. Experts stress the importance of robust email authentication, particularly DMARC, as a primary tool for monitoring and verifying mail streams.
Key opinions
- Forwarding is key: Experts consistently identify email forwarding by recipients as the leading cause of unexpected IP appearances. When emails are forwarded, they pass through different mail transfer agents (MTAs), which can introduce new IPs into reputation data.
- DMARC for visibility: Implementing and monitoring DMARC is considered crucial. DMARC reports provide a comprehensive overview of all IP addresses attempting to send email on behalf of your domain, including those associated with forwarding chains.
- ISP involvement: If the unexpected IP belongs to a major ISP, it strongly indicates forwarding. These ISPs often use their own servers to re-route forwarded mail.
- Not necessarily spoofing: The presence of an unexpected IP does not automatically mean your domain is being spoofed. DMARC helps distinguish between legitimate forwarding and unauthorized sending.
Key considerations
- Policy enforcement: Experts recommend a strong DMARC policy (e.g., p=quarantine or p=reject) coupled with careful monitoring, to ensure that only authorized IPs successfully send email for your domain.
- SPF failure analysis: Email forwarding typically breaks SPF alignment, leading to SPF failures in DMARC reports. This is a common indicator of legitimate forwarding.
- Investigate unusual sources: If the unexpected IP does not belong to a major ISP or a known legitimate forwarding service, further investigation is warranted to rule out unauthorized sending.
- Holistic view: While Senderscore is a useful tool, experts advise looking at the full picture of your email deliverability, including bounce rates, spam complaints, and other reputation signals. For more insights on this topic, refer to the Spam Resource blog.
Expert view
A deliverability expert from Email Geeks suggests that DMARC reporting can provide additional assurance against domain spoofing from unexpected IP addresses.
Expert view
A deliverability expert from Email Geeks clarifies that DMARC records should be checked on the main domain for comprehensive oversight.
What the documentation says
Technical documentation and research on email deliverability consistently highlight the complex nature of IP reputation and the various factors that can influence it. For dedicated IPs, the responsibility of maintaining a healthy reputation lies squarely with the sender. Documentation often details how even seemingly minor factors, such as recipient email forwarding, can affect how an IP is perceived by reputation systems like Senderscore.
Key findings
- Dedicated IP control: Documentation confirms that dedicated IPs offer senders exclusive control over their reputation, but this also means bearing sole responsibility for building and maintaining it through consistent and quality sending practices.
- IP warming requirement: New dedicated IPs start with an unknown reputation and require a warming process, gradually increasing sending volume to establish a positive history.
- Reputation factors: IP reputation is determined by sending history, including metrics like bounce rates, spam complaint rates, and presence on blacklists (or blocklists). These factors are crucial for ISPs in deciding how to treat incoming emails.
- DMARC for visibility: Technical specifications for DMARC underscore its role in providing senders with visibility into all email streams that claim to originate from their domain, which can help in identifying unexpected IPs.
Key considerations
- Proactive monitoring: Documentation encourages regular checking of IP and domain against public blocklists (blacklists) as a fundamental part of maintaining good deliverability. This can help detect unexpected listings early.
- Review sending logs: Any unexpected IP activity should prompt a thorough review of internal sending logs and DNS records to rule out internal misconfigurations or unauthorized access.
- Understand email routing: Be aware that email routing can involve intermediate servers, especially with forwarding services or complex network configurations, which can introduce different IPs into reputation reports. Learn more about how dedicated IPs are managed in enterprise settings.
- Authentication protocols: Proper implementation of email authentication protocols like SPF, DKIM, and DMARC is crucial for accurately attributing email to its legitimate sender and mitigating the impact of unexpected IPs.
Technical article
Documentation from AWS explains that dedicated IP addresses provide exclusive control over sending reputation, which entails sole responsibility for building and maintaining it through consistent sending and proper IP warming.
Technical article
Documentation from Twilio advises that sender reputation monitoring encompasses bounce rates, spam complaints, and blocklist presence, and unexpected IP activity should trigger a review of sending logs and DNS records.
Related resources
15 resources
Related pages
A simple guide to DMARC, SPF, and DKIM
How to safely transition your DMARC policy to quarantine or reject
What are common email deliverability issues during new IP and subdomain warmup after ESP migration?
What happens when your ip gets blocklisted?
Why Your Emails Are Going to Spam in 2024 and How to Fix It
Email Deliverability Issues: Getting Your Messages to the Inbox in 2025
An in-depth guide to email blocklists
Understanding and troubleshooting DMARC reports from Google and Yahoo
The benefits of implementing DMARC
Demystifying the SPF TempError in your DMARC reports
