Your Klaviyo Spam Complaint Rate Is a Ticking Time Bomb — Here's How to Fix It

Most Shopify brands don't think about spam complaints until it's too late. By the time your deliverability tanks, the damage is already done — and clawing back sender reputation takes weeks, sometimes months.

This article breaks down what spam complaints actually are, why they matter more than almost any other email metric, and the exact system we use at Redot to keep every client's complaint rate well below the critical threshold.

What Is a Spam Complaint Rate?

Your spam complaint rate is the percentage of recipients who hit the "Report Spam" or "Mark as Junk" button after receiving your email.

The formula is simple: Complaints ÷ Delivered Emails = Complaint Rate

If you send 10,000 emails and 10 people mark it as spam, your complaint rate is 0.10%.

That might sound tiny. It's not. It's already above the danger zone.

Why 0.08% Is the Line in the Sand

Google and Yahoo updated their sender requirements in early 2024. The new threshold is clear: keep your spam complaint rate below 0.08%, or face consequences.

Those consequences include throttled delivery (your emails get delayed), inbox placement drops (more emails land in spam), and in severe cases, temporary blocks where your emails simply don't get delivered at all.

For context, our Love Blanket case study maintained a complaint rate of 0.03% — well below the threshold — while sending 100+ campaigns over 12 months. That didn't happen by accident.

The 3 Root Causes of High Complaint Rates

1. Sending to Unengaged Subscribers

This is the number one cause. If someone hasn't opened your emails in 90+ days, they've mentally unsubscribed. When they finally see one of your emails, they don't look for the unsubscribe link — they hit spam.

The fix is strict engagement-based segmentation. At Redot, every client account has these segments built from day one:

• Engaged 14 days — opened or clicked in the last 14 days
• Engaged 30 days — your primary campaign audience
• Engaged 60 days — secondary, lower frequency
• Engaged 90 days — minimal sending, re-engagement attempts only
• Unengaged 90+ days — no campaigns, sunset flow only

2. Unclear or Missing Expectations at Signup

If subscribers don't know what they're signing up for, they'll complain when emails arrive. Your signup form should set clear expectations about what you'll send and how often.

The Welcome Flow also plays a role here. A strong Welcome Series that delivers value immediately reduces complaints because subscribers recognize and anticipate your emails.

3. No Easy Unsubscribe Option

If people can't find the unsubscribe link, they'll use the spam button instead. Make unsubscribing easy and obvious. A visible unsubscribe link in the header actually reduces complaints — counterintuitive, but true.

The Sending Cadence Rules That Protect You

Not everyone on your list should get the same number of emails. Here's the cadence framework we follow:

This tiered approach means your most engaged subscribers get the most content, while less engaged subscribers get just enough to stay warm without feeling bombarded.

Build a Sunset Flow — Your Safety Net

A Sunset Flow is the last line of defense before an unengaged subscriber hurts your deliverability. Here's how it works:

The trigger fires when someone hasn't opened or clicked any email in 90 days. The sequence is usually 2-3 emails with increasingly direct subject lines.

Something like "We miss you — here's 15% off" followed by "Last chance before we remove you from our list."

If they don't engage after the final email, suppress them automatically. It feels counterintuitive to shrink your list, but a smaller, engaged list always outperforms a large, unengaged one.

Monitor Weekly, Not Monthly

Don't wait for monthly reports to check your complaint rate. In Klaviyo, you can see complaint rates per campaign in the campaign analytics. Check it after every send for the first 48 hours.

If you see a spike, stop and investigate before the next send. Was it a new segment? A misleading subject line? A send to a less engaged group?

The Bottom Line

Your spam complaint rate is the single most important deliverability metric. It's more important than open rates, more important than click rates, and definitely more important than list size.

Keep it below 0.08%. Build your segments properly. Use a sunset flow. And never, ever send to an unengaged list.

Your future deliverability depends on the decisions you make today.