Summary
Spam spikes in Google Postmaster Tools on days with no email sends are complex and multi-faceted. Several factors contribute, including the delayed reporting of spam complaints, where past sends influence current metrics. Changes in user behavior, aggressive spam filtering by ISPs, and issues with list hygiene (stale email addresses or spam traps) also play a role. Technical issues like inconsistencies in sender reputation, authentication protocols (SPF, DKIM, DMARC) failures, and delayed Spam Confidence Level (SCL) adjustments can lead to spam filtering even without active sending. Additionally, the presence of compromised email accounts sending unauthorized emails, or shared IP addresses where other senders' poor practices affect your reputation can lead to spam spikes. Finally, spoofing and list bombing attacks from third parties can further exacerbate the issue. Machine learning algorithms by email providers can sometimes cope with these spikes, so analysis of feedback loops, monitoring sender reputation, and securing email systems are important.
Key findings
- Complaint Delays: Spam reporting is often delayed, influencing current metrics.
- External Factors: ISPs update filters, user behaviour changes, and third party spoofing impacts spam filters.
- List Issues: Stale emails or spam traps cause complaints.
- Reputation Problems: Poor sender history and inconsistent authentication hurt deliverability.
- Technical Problems: Authentication issues or SCL adjustments lead to spam filtering.
- Security Issues: Compromised accounts and shared IP's contribute to the issue.
- Algorithm Management: Email providers Machine learning systems are designed to cope with spikes.
Key considerations
- Monitor Reputation: Regularly check sender reputation metrics, bounce rates, and complaints.
- Secure System: Audit and secure email systems to avoid compromisation.
- Review Authentication: Ensure SPF, DKIM, and DMARC records are properly configured.
- Hygiene: Implement strong email list hygiene practices to remove old or invalid accounts.
- Analyze Feedback: Analyze feedback loops to pinpoint spam complaint origins.
- Verify Dashboard: Verify dashboard accuracy with your ESP to eliminate misreporting.
- Implement DMARC: Use DMARC to protect against domain spoofing.
- Consider Shared IP: If on a shared IP, be aware of other users' sending behaviour.
What email marketers say
10 marketer opinions
Spam spikes in Google Postmaster Tools on days with no email sends can be attributed to several factors. These include delayed feedback loops from prior sends, potential spoofing or list bombing attacks, changes in user behavior or aggressive filtering by ISPs, poor list hygiene involving stale or trap email addresses, inconsistencies in sender reputation and authentication protocols (SPF, DKIM, DMARC), and the possibility of a compromised email system sending unauthorized emails. Shared IP addresses and the actions of other senders can also impact your reputation. Essentially, delayed reporting, external abuse, and ongoing maintenance of sender reputation are key considerations.
Key opinions
- Delayed Feedback: Spam complaints reported today might stem from emails sent previously.
- Spoofing/Bombing: Malicious actors could be using your domain or adding your email to many lists.
- External Factors: ISPs may have updated filtering, and user behavior can change.
- List Hygiene: Old or invalid addresses can trigger spam complaints.
- Reputation Issues: Inconsistent authentication or sender history can affect deliverability.
- Compromised System: Unauthorized emails could be originating from your system.
- Shared IP: Other senders on your IP can affect your spam rate.
Key considerations
- Review Feedback Loops: Analyze feedback loops for insights into spam complaints.
- Implement DMARC: Use DMARC to prevent domain spoofing.
- Monitor Reputation: Track sender reputation metrics and authentication protocols.
- Clean Email Lists: Regularly remove inactive or problematic email addresses.
- Secure Systems: Audit user access and secure email systems against unauthorized access.
- Check for List Bombing: Implement CAPTCHA and double opt-in on forms.
Marketer view
Email marketer from Email on Acid answers that inconsistencies in sender reputation, authentication protocols (SPF, DKIM, DMARC), and content quality can cumulatively impact spam scores, even when no emails are actively being sent. Ongoing reputation damage affects future assessments.
31 Jul 2024 - Email on Acid
Marketer view
Email marketer from Hubspot shares that a sender's reputation is based on the history of sending and how recipients interact with emails. If your sender reputation decreases, email providers are more likely to mark the email as spam.
20 Aug 2024 - Hubspot
What the experts say
4 expert opinions
Spam spikes in Google Postmaster Tools, even on days without email sends, can be influenced by delayed reporting of complaints and the impact of even a single complaint on low-volume days. Machine learning systems are designed to handle these fluctuations. Additionally, the issue may stem from unauthorized third parties sending emails that appear to originate from your domain, underscoring the importance of reviewing feedback loops to identify the source of spam complaints.
Key opinions
- Delayed Reporting: Spam complaints often reflect past sends, not current activity.
- Single Complaint Impact: A single spam report can disproportionately affect rates on low-volume days.
- Third-Party Abuse: Unauthorized senders using your domain can damage your reputation.
- Machine Learning Handling: Machine learning systems are designed to cope with spikes.
Key considerations
- Review Feedback Loops: Analyze feedback loops to identify the origin of spam complaints.
- Investigate Unauthorized Sending: Check for and prevent unauthorized use of your domain.
- Don't Panic: Recognize that ML algorithms are trained to manage the normal level of complaint spikes.
Expert view
Expert from Email Geeks explains that most complaints are reported the day they’re reported, not the day the mail was sent. A single complaint on a low-volume day can skew complaint rates.
3 Sep 2024 - Email Geeks
Expert view
Expert from Spam Resource explains that the problem might not be you. Are there third parties sending mail that looks like it's coming from your domain? If they're not authenticating properly, that could be hurting you.
28 Nov 2024 - Spam Resource
What the documentation says
5 technical articles
Spam spikes in Google Postmaster Tools during periods of no email sends are attributed to several technical factors. These include delayed reporting of spam complaints, affecting metrics out of sync with send times; adjustments in Spam Confidence Levels (SCL) by email providers; and persistent issues with sender reputation, caused by high bounce or complaint rates. DNS configuration problems such as SPF or DKIM failures can also trigger spam filters, even when no emails are being actively sent. Analyzing feedback loops, sender reputation metrics, and content are critical for understanding these spikes.
Key findings
- Delayed Complaints: Spam reports are not always immediate; prior sends can impact current metrics.
- SCL Adjustments: Email providers may retroactively reclassify emails as spam, affecting past results.
- Reputation Impact: Poor sender reputation leads to spam filtering, regardless of send volume.
- DNS Issues: SPF and DKIM failures can trigger spam filters, leading to spikes.
Key considerations
- Analyze Feedback Loops: Scrutinize feedback loops to understand spam complaint sources.
- Monitor Reputation Metrics: Track sender reputation, bounce rates, and complaint rates.
- Review DNS Configuration: Ensure SPF and DKIM records are correctly configured.
- Content Analysis: Review Email Content to improve quality of messages.
Technical article
Documentation from Microsoft explains that delayed Spam Confidence Level (SCL) adjustments could contribute to spam spikes. Messages initially categorized as non-spam might later be re-evaluated, affecting your Postmaster Tools metrics on subsequent days.
2 Nov 2023 - Microsoft
Technical article
Documentation from AWS Simple Email Service (SES) explains that consistently poor sender reputation metrics, such as high bounce or complaint rates, can trigger spam filtering even on days with minimal or no email activity. ISPs use these metrics to determine deliverability.
12 Jun 2025 - AWS
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