Here’s the conventional wisdom you’ve probably heard a hundred times: send fewer emails, get fewer spam complaints.
It sounds obvious. It makes intuitive sense. And it’s mostly wrong.
InboxEagle analyzed 31,586 real sending programs to understand how email sending frequency actually correlates with spam rates across ecommerce brands. What we found challenges the “just send less” narrative — and reveals the real driver behind elevated complaint rates.
Spoiler: it’s not frequency. It’s what you’re doing with that frequency.
InboxEagle Frequency & Spam Rate Study
What the Data Actually Shows
We segmented 31,586 sending programs into three groups based on their send volume and measured the average spam rate for each group.
Here’s what we found:
- Low-send group (≤7 avg sends, averaging 2.46 sends): 18.04% avg spam rate
- Mid-send group (14–45 avg sends, averaging 26.83 sends): 23.34% avg spam rate
- High-send group (≥157 avg sends, averaging 441.87 sends): 15.02% avg spam rate
Read that again. The senders sending the most emails — an average of 441 per program — had the lowest spam rate of the three groups.
The mid-frequency senders were the worst performers. They send enough to generate real complaints, but typically lack the list hygiene discipline and engagement segmentation that high-volume programs are forced to develop.
When we ran the Pearson correlation across the full dataset, we got -0.04 — statistically, no linear relationship between send volume and spam rate. The Spearman correlation came in at 0.262, indicating a modest rank-based relationship, but far from the strong causal link most marketers assume.
Frequency isn’t the villain here. Poor sending practices are.
Why High-Volume Senders Win on Spam Rates
Here’s what’s really going on. Brands sending at serious scale — 157+ emails per program in our dataset — cannot afford to ignore deliverability. One bad campaign at volume doesn’t just hurt a single send; it can torch a domain reputation built over years.
So high-volume senders invest in the infrastructure that actually matters:
- Aggressive list segmentation — they don’t blast the full list; they send to active subscribers first
- Sunset flows — contacts who haven’t engaged in 60–90 days are suppressed or put through re-engagement
- Preference centers — subscribers choose their own frequency, which aligns expectations and reduces complaints
- Real-time complaint monitoring — they watch Google Postmaster Tools and suppress complainers immediately
Mid-frequency senders skip these steps. They’re sending often enough to accumulate complaints, but not often enough to feel the reputational pain that forces them to clean things up.
That’s the trap. And a lot of Klaviyo users fall into it.
The Frequency-Spam Relationship Is Conditional
The data doesn’t say frequency is irrelevant. It says frequency alone doesn’t predict spam rate — but frequency combined with poor practices is a different story.
Look at the top 10% of senders in our dataset (those sending ≥157 times, averaging 441 sends):
- 25.24% of them had spam rates at or above 20
- 10.8% had spam rates at or above 50
Compare that to the rest of the senders:
- 29.4% had spam rates at or above 20
- 19.7% had spam rates at or above 50
High-volume senders still have outliers with serious problems — but proportionally, they have fewer of them. The discipline required to operate at scale improves outcomes across the board.
The conclusion? If you’re sending at high frequency with a clean, engaged list, you’re probably fine. If you’re ramping frequency without improving your list quality and suppression workflows, you’re about to have a very bad time.
What Google Says About Spam Complaint Thresholds
Let’s ground this in what actually triggers deliverability consequences.
Google’s bulk sender guidelines require keeping your spam complaint rate below 0.10% in Postmaster Tools as a best practice. Rates above 0.30% can result in outright rejection of your messages. Starting February 2024, Gmail enforced these standards for anyone sending 5,000+ messages per day — and in November 2025, enforcement escalated further with permanent rejection codes for non-compliant traffic.
Klaviyo’s own guidance aligns with this: sending too frequently to unengaged profiles makes recipients far more likely to hit the spam button. Their recommendation is to base cadence on engagement — daily sends for highly engaged subscribers, weekly or less for anyone who hasn’t opened in 90+ days.
The 0.10% threshold sounds easy to stay under. But at volume, it adds up fast. If you’re sending 500,000 emails and 500 people mark you as spam, you’ve hit 0.10% exactly. That’s one poorly-targeted campaign to a stale segment.
The Real Drivers of Spam Complaints in Ecommerce
Based on the InboxEagle data and the research backing it, here’s where spam complaints actually come from:
1. Sending to disengaged lists Subscribers who stopped opening six months ago haven’t forgotten you — they just don’t want your emails anymore. When you keep sending, they start marking spam instead of unsubscribing. According to Mailgun, 50% of users resort to the spam button simply because they can’t find an easy unsubscribe link.
2. No suppression workflows Every complaint is a signal. If you don’t suppress complainers immediately and keep them off future sends, you compound the damage with every campaign.
3. Irrelevant content at the wrong cadence It’s not just how often you send — it’s whether the send feels relevant to the recipient at that moment. A daily email from a brand you love doesn’t feel like spam. A weekly email from a brand you forgot you signed up for does.
4. Jumping frequency without ramping Suddenly going from one campaign per month to daily sends is a red flag for ISPs. Consistent, predictable sending behavior is what builds trust with mailbox providers. Erratic volume spikes — whether from frequency or list growth — trigger filters. If you’re scaling into peak season, read how to protect your sender reputation during volume spikes.
What This Means for Your Klaviyo Program
If you’re managing an ecommerce email program in Klaviyo, here’s how to apply this data practically:
- Don’t suppress frequency — suppress disengagement. Before you cut sends, cut your inactive subscribers. The InboxEagle data shows low-send programs aren’t automatically safe (18.04% spam rate). List quality matters more than send count.
- Build a sunset flow. Any contact who hasn’t opened in 90 days goes into a re-engagement sequence. If they don’t engage with that, they get suppressed. This single workflow dramatically reduces complaint rates at scale.
- Use Smart Sending. Klaviyo’s Smart Sending feature prevents any single contact from receiving too many emails in a short window. It’s a basic safeguard that’s often left off.
- Watch your mid-frequency segments closely. Our data flags mid-frequency senders (14–45 sends) as the highest-risk group. If that describes your current cadence, your suppression and segmentation workflows need to be solid before you scale.
- Track your inbox placement, not just opens. Open rates are an unreliable proxy for deliverability. Learn why in Why Open Rate Is a Misleading Deliverability Metric.
The Bottom Line
More emails doesn’t automatically mean more spam complaints. The data is clear on that.
What drives spam complaints is frequency without discipline — sending volume that’s not backed by list hygiene, engagement segmentation, and real-time complaint monitoring. High-volume senders who get this right consistently outperform mid-frequency senders who ignore it.
If you’re hitting elevated spam rates, don’t just cut your send frequency. Audit your list quality, set up proper suppression workflows, and start watching your complaint data in Google Postmaster Tools after every send. That’s where the leverage is.
Want to know where your sending program stands right now?
InboxEagle monitors your spam complaint rates, inbox placement, and sender reputation across Gmail, Yahoo, and Outlook — in real time, not after the damage is done.
Note: Content created with the help of AI and human edited and fact-checked to avoid AI hallucinations.
