Above 0.1% Gmail starts marking sender domain. KL03 fires; investigate immediately.
At a glance
The percentage of recipients who hit “Mark as spam” or “Report junk” on a campaign in the period. Computed as SUM(spam_complaints) ÷ SUM(recipients) × 100 aggregated across every campaign. Spam rate is the most consequential deliverability metric on the entire dashboard: above 0.1% Gmail starts placing the sender into the spam folder for the recipient’s whole network, and once that happens it takes 30-60 days of clean sending to recover.
Calculation
Calculated automatically from your Klaviyo data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.Worked example
A fashion brand with a 220,000-subscriber list runs the following campaigns over the 30-day window 14 Mar 26 to 12 Apr 26:- 0.143% is already over the line. Gmail’s threshold is 0.1%. The merchant is in territory where Gmail will start placing sends into the spam folder for an increasing fraction of Gmail recipients. The damage isn’t visible immediately, it shows up as falling open rates 1-2 weeks later as more sends silently route to spam.
- The flash sale at 0.17% drove most of the volume. A double-send of a heavy-discount campaign generated 612 of the 1,053 complaints. Frequency is the most reliable trigger of spam complaints: the same campaign sent twice within a few days dramatically increases complaints because a meaningful slice of recipients see the second send as harassment regardless of how good the offer is.
- The re-engagement and win-back are catastrophic on a small base. 0.3% and 0.5% respectively are the kind of complaint rates that get sender domains delisted in days, not weeks. Win-back to dormant subscribers is high-risk by definition; doing it through the same sending domain as your healthy promotional sends contaminates everything. Use a separate subdomain.
- The blended figure hides a per-campaign emergency. Looking only at the 0.143% blended account rate, the merchant might think “small over the line, manageable”. Looking at the 0.5% win-back, they should pause the campaign immediately. Always read this card alongside the per-campaign view in Klaviyo’s dashboard.
- At 0.143% there’s a 14-day window before reputation damage shows up in revenue. Gmail’s domain reputation is sticky; one bad month doesn’t kill it instantly. But the corrective action (stop sending to dormant cohorts, audit list source quality, slow cadence) should happen this week, not after open rates drop. By the time opens drop, the merchant has already lost 2-3 weeks of revenue and Gmail recovery takes 30-60 days.
Sibling cards merchants should reference together
Spam rate is the most consequential deliverability metric. Pair it with these:Reconciling against the vendor’s own dashboard
Where to look in Klaviyo: Klaviyo → Analytics → Deliverability for the headline spam complaint rate over time. Klaviyo’s own dashboard breaks this down per-campaign and per-ISP, this card sums it across all campaigns to a single account-level figure. The figures should match this card to within a few thousandths of a percent (this is a 4-decimal-precision metric). Other Klaviyo views that look like the same number but aren’t:- Campaigns → individual campaign view → “Performance”: per-campaign spam rate only. This card aggregates across all campaigns.
- Account Settings → Sender Reputation: a blended score that mixes spam, bounce, engagement, authentication. Not the same as raw spam rate.
- Reports → Custom Reports: configurable to match this metric. Default reports differ.
- Gmail Postmaster Tools: ISP-side view from Gmail. Should track directionally but not numerically. Gmail uses a different denominator (delivered to Gmail vs total recipients).
Cross-connector reconciliation:
Spam complaint rate is a Klaviyo-internal metric. There is no commerce platform or analytics tool that surfaces a directly comparable figure. The closest cross-references are:
Known limitations / merchant FAQs
My spam rate is 0.15%, what do I do right now? Three actions in the next 24 hours: (a) pause the campaign with the highest individual spam rate (open Klaviyo dashboard, sort campaigns by spam rate descending); (b) suppress everyone who has not opened an email in 90+ days, this is the cohort most likely to mark future sends as spam; (c) cut send frequency for the next 7 days to engaged segments only (opened or clicked in last 30 days). Do not “ride it out”, every additional send at 0.15% deepens the reputation damage with Gmail. Is this the same as Gmail Postmaster Tools’ spam rate? Directionally yes, numerically no. Postmaster Tools shows Gmail-only complaint rate computed against Gmail-delivered messages. This card shows all-ISP complaints against all-recipient sends. If 60% of your list is Gmail, the two figures will be similar; if your list is heavily Outlook or Apple, they’ll diverge significantly. Use Postmaster for Gmail-specific diagnosis, this card for blended account health. What’s the difference between spam complaints and unsubscribes? A spam complaint is the recipient clicking “Report spam” or “Mark as junk”, which signals to the ISP that the sender shouldn’t be allowed in the inbox at all. An unsubscribe is the recipient clicking the unsubscribe link in the footer, which signals to you that they want off the list. Both remove the address from future sends. Spam complaints damage your reputation; unsubscribes don’t. A healthy account has unsub rate 5-20× higher than spam rate (e.g. 1% unsub, 0.05% spam) because the unsubscribe path absorbs dissatisfaction before it reaches the spam button. How long does it take to recover from a spam-rate breach? Depends how high it went and for how long. Brief blips above 0.1% recover in 1-2 weeks of clean sending. Sustained breaches above 0.3% take 30-60 days because Gmail’s domain reputation algorithm lags. Above 0.5% the most reliable recovery is to migrate to a fresh sending subdomain and warm it slowly over 4-6 weeks, leaving the contaminated domain for transactional-only mail. Does this card include flow spam complaints? No, this card aggregatescampaign-values-reports only. Flow spam complaints are tracked separately in flow-values-reports and aren’t pulled here. For most merchants, campaigns generate >90% of total complaints anyway, so the campaign-only figure is a reliable proxy. If your account is flow-heavy (high welcome flow volume, high abandoned-cart volume to a non-engaged audience), the true account-wide rate may be slightly higher.
Why did my spam rate spike on a campaign that performed well otherwise?
The most common cause is “unsubscribe friction”. If the unsubscribe link is buried, broken, or requires login, recipients hit “Report spam” instead because it’s faster and removes them from the list immediately. Audit the email template: the unsubscribe link should be visible above the fold of the footer, in plain text, and one click should remove the recipient (no “are you sure” page). The second most common cause is unrecognised sender, recipients who don’t remember signing up report unfamiliar mail as spam. Add a clear “You’re receiving this because you signed up at yourstore.com” line above the footer.
Does sending from a custom subdomain help?
Yes, materially. With a custom subdomain (mail.yourstore.com) reputation damage is contained. With shared Klaviyo infrastructure, your spam rate affects only your share of the shared IP pool, which Klaviyo manages defensively. Custom subdomains let you separate marketing sends (higher complaint risk) from transactional sends (low complaint risk) so a marketing-side reputation hit doesn’t disrupt order confirmations. Recommended above 100,000 sends per month or any time your spam rate has been above 0.1% in the last 90 days.
My re-engagement campaign caused the spam spike, should I stop running them?
No, but isolate them. Re-engagement to dormant subscribers is high-risk by definition; the recipients haven’t engaged in 90+ days and a meaningful fraction will report unfamiliar mail as spam. Best practice: send re-engagement from a dedicated subdomain (e.g. reengagement.yourstore.com) that’s separate from your healthy marketing sends, send to small batches (5,000 at a time) over a week, and suppress non-openers aggressively after the campaign. The numbers from the worked example above (0.5% on win-back) are typical and acceptable on an isolated subdomain; they’re catastrophic on the main domain.
Why does this matter so much more than open rate or click rate?
Spam rate is the only metric on the dashboard that directly damages future sends to recipients you haven’t sent to yet. Low open rate means recipients ignored you; spam rate means recipients told the ISP to stop you reaching others. Above 0.1% the consequences extend to your full list, not just the campaign that caused the spike.