Why are my emails going to spam even with a low spam rate?
Michael Ko
Co-founder & CEO, Suped
Published 9 Jul 2025
Updated 15 Aug 2025
8 min read
It can be incredibly frustrating when your emails are landing in spam, especially when your analytics, like Google Postmaster Tools, report a consistently low spam rate. You might be seeing figures like 0.1% or 0.2% and still wonder, "Why are my emails going to spam?" This paradox is more common than you might think and often points to underlying issues beyond just the explicit spam complaint rate.
The spam rate shown in tools like Google Postmaster reflects the percentage of your emails marked as spam by recipients or automatically classified by spam filters. A low rate might suggest your emails aren't being mass-reported, but deliverability is a complex dance between many factors. A low spam rate doesn't guarantee inbox placement for every single email.
Even with a low spam rate, issues like poor engagement, specific recipient filters, or subtle technical misconfigurations can divert your messages to the junk folder. Understanding these hidden factors is key to improving your overall inbox placement.
Sender reputation and engagement
One of the most common reasons emails go to spam, despite a low reported spam rate, is a negative sender reputation. While your explicit spam complaints might be low, other signals contribute to your reputation score with internet service providers (ISPs).
ISPs like Gmail and Microsoft (Outlook/Hotmail) use sophisticated algorithms to evaluate a sender's trustworthiness. These algorithms consider metrics such as open rates, click-through rates, reply rates, unsubscribes, and even emails being deleted without being opened. A consistent lack of positive engagement can signal to an ISP that your emails are not desired, leading them to be filtered to spam, even if no explicit complaint is filed. This is particularly relevant when you might have good authentication and a low spam rate.
Your domain's reputation is built over time through consistent sending practices and recipient interaction. If you've previously sent to unengaged lists or had periods of inconsistent volume, that historical data can linger. ISPs might also categorize your emails based on what they perceive as spammy content patterns, even if your intentions are legitimate. This is a common challenge for new domains or subdomains warming up.
Monitoring your sender reputation through tools like Google Postmaster Tools can provide insights, but even a good reputation score there doesn't always tell the whole story for other mailbox providers. You need a holistic view of deliverability.
Technical authentication issues
While you might have SPF, DKIM, and DMARC records in place, improper configuration or alignment issues can still cause problems. Even if your emails technically pass authentication checks, subtle misconfigurations can lead to deliverability issues.
For example, SPF records can become too long (exceeding the 10 DNS lookup limit), leading to SPF PermError or TempError issues. DKIM keys can expire or be misconfigured, resulting in DKIM body hash mismatch failures. DMARC, while providing a policy, relies on SPF and DKIM passing and aligning. If one of these fails alignment, DMARC will also fail, even if the base SPF or DKIM passes.
These technical nuances can often go unnoticed if you're only performing basic checks. A robust email authentication setup, including SPF, DKIM, and DMARC, is fundamental to establishing trust with ISPs and ensuring your emails reach the inbox. Without it, your emails might be flagged, even with a low spam complaint rate, because the receiving server can't verify your identity.
Check SPF lookups: Ensure your SPF record does not exceed the 10 DNS lookup limit, as this can cause failures.
Verify DKIM selectors: Confirm that your DKIM selectors are active and correctly configured.
DMARC alignment: Ensure your DMARC policy is set up correctly and that SPF and DKIM are aligning with it. For detailed guidance on setting this up, consult our simple guide to DMARC, SPF, and DKIM.
Poor list hygiene and spam traps
Your email list quality plays a significant role in deliverability. Even with a low spam rate, if your list contains a high percentage of inactive subscribers, abandoned email addresses, or spam traps, it can severely harm your sender reputation. Spam traps are email addresses used by ISPs and blocklist operators to identify senders who are not maintaining clean lists. Hitting a spam trap, even once, can instantly damage your reputation and lead to blacklisting (or blocklisting).
Emails sent to unengaged users who consistently don't open or click your messages also negatively impact your sender score. ISPs interpret this lack of engagement as a sign that your emails are not valuable or wanted. This can lead to your emails being filtered to the spam folder for those specific recipients, and over time, for your entire sending domain.
Regularly cleaning your email list to remove inactive subscribers, hard bounces, and known spam traps is crucial. Implementing a double opt-in process for new subscribers can also help ensure you're only sending to genuinely interested recipients, thus improving overall engagement and reducing the risk of hitting spam traps. If you're experiencing issues with specific email providers like Yahoo, consider how your list hygiene impacts their filters. Sometimes, even with high open rates on other platforms, emails can still end up in spam for certain providers due to historical data or specific filter sensitivities.
Content and formatting issues
Even with perfect authentication and a clean list, the content of your emails can trigger spam filters. Certain keywords, excessive use of all caps, too many exclamation marks, or misleading subject lines can flag your emails. Overly promotional language or a high ratio of images to text can also be red flags for sophisticated spam filters.
Furthermore, embedding problematic links or using shortened URLs without proper tracking can also lead to issues. ISPs are increasingly vigilant about phishing and malware, so any link that appears suspicious can lead to immediate spam placement. It's not just about what you say, but also how your email is structured and what external elements it includes. Remember that a low spam complaint rate doesn't mean your content is immune to algorithmic filtering.
Content pitfalls
Spam trigger words: Using excessive sales-oriented or suspicious phrases.
Poor formatting: Broken HTML, disproportionate image-to-text ratio, or large attachments.
Deceptive subject lines: Not accurately reflecting the email's content.
Malicious or suspicious links: Links to untrustworthy domains or unverified shortened URLs.
Delayed complaints and volume impact
Even if your email activity is low, a sudden spike in negative engagement metrics on a day you didn't send emails can inflate your perceived spam rate. This often happens because complaints or unsubscribes from previously sent campaigns are reported with a delay. So, while you didn't send on March 10th, the 1.8% spam rate might reflect delayed reports from an earlier send, especially if that campaign saw a higher-than-usual unsubscribe rate.
This effect is amplified with low sending volumes. If you send 100,000 emails and get 10 complaints (0.01%), that's low. But if you send 100 emails and get 2 complaints (2%), the rate skyrockets. ISPs can be very sensitive to these percentage shifts, especially if they are already scrutinizing your sender reputation.
Additionally, external factors can influence recipient behavior. For instance, if people are spending more time at home, they might be more likely to triage their inboxes, leading to a higher propensity to unsubscribe or mark emails as spam, even from senders they've tolerated before. This increased scrutiny, even without a change in your sending habits, can lead to seemingly inexplicable spikes in negative metrics.
Conclusion
Resolving deliverability issues when your spam rate is low requires a comprehensive approach. It's rarely a single problem, but rather a combination of factors subtly impacting your sender score and inbox placement.
By actively monitoring all aspects of your email program, from technical setup to content and recipient engagement, you can identify the root causes. Remember that ISPs are constantly evolving their filtering mechanisms, making continuous optimization a necessity for successful email marketing.
Views from the trenches
Best practices
Maintain a consistent sending volume to avoid sudden spikes that can trigger filters.
Regularly clean your email list, removing inactive and unengaged subscribers to improve overall deliverability.
Implement double opt-in for all new subscribers to ensure high-quality, permission-based lists.
Personalize email content and segment audiences to increase engagement and reduce spam complaints.
Common pitfalls
Ignoring subtle dips in engagement metrics like open rates or click-through rates, which are key deliverability signals.
Over-relying on a single metric, such as a low spam rate, without considering other reputation factors.
Sending to old, uncleaned lists, risking hitting spam traps and damaging sender reputation.
Using generic or overly promotional subject lines and content that can trigger spam filters.
Expert tips
Use a diverse set of email engagement metrics, not just spam rate, to assess deliverability.
Segment your audience and tailor content to specific interests to boost engagement.
Regularly check for DMARC reporting to identify authentication failures and sources of unauthenticated email.
Pay close attention to changes in recipient behavior, as these can impact how ISPs filter your mail.
Marketer view
Marketer from Email Geeks says that low volume combined with complaints from previous days can cause spikes in spam rates. One or two days of high rates usually do not have a long-term impact.
2020-03-20 - Email Geeks
Marketer view
Marketer from Email Geeks says to investigate what was sent just before the spike in spam complaints, as there might be a delayed reaction from recipients.
Gmail and 
Microsoft (Outlook/Hotmail) use sophisticated algorithms to evaluate a sender's trustworthiness. These algorithms consider metrics such as open rates, click-through rates, reply rates, unsubscribes, and even emails being deleted without being opened. A consistent lack of positive engagement can signal to an ISP that your emails are not desired, leading them to be filtered to spam, even if no explicit complaint is filed. This is particularly relevant when you might have good authentication and a low spam rate.
Yahoo, consider how your list hygiene impacts their filters. Sometimes, even with high open rates on other platforms, emails can still end up in spam for certain providers due to historical data or specific filter sensitivities.
