Fixing Low Email Engagement · Part 3: How to prevent hard bounces before they happen
- Judith Prugger
- Aug 11
- 2 min read
Aug 11th, 2025
Hard bounces = invalid email addresses. They hurt deliverability the moment they happen — even though Klaviyo suppresses them after 1 send.
Here’s how to keep them off your list entirely:
1️⃣ Enable double opt-in
Requires new subscribers to click a confirmation link before being added to your list.
Blocks fake or mistyped addresses from ever entering.
Free and low effort to set up in Klaviyo.
Trade-off: Fewer signups, but higher quality and better engagement.
2️⃣ Add real-time email validation
Integrates with Klaviyo or your signup forms to check every new email address in real time.
Flags typos, fakes, and role-based addresses (like info@ or sales@) before they hit your list.
Example: ZeroBounce starts at ~$16/month for up to 2,000 email validations — cheap insurance compared to the cost of sending to bad addresses.
Works automatically in the background once connected, so no ongoing manual cleanup.
3️⃣ Review traffic sources
Signups from low-intent sources (like giveaways or contests) are more likely to bounce.
Use stricter validation (e.g., double opt-in or a real-time verification tool) or filter these signups before adding them to your main list.
Next steps & what's coming
If your Klaviyo deliverability score is below ~90 or your bounce rate is above 1% (and definitely if it’s 2%+), it’s time to act.
Above 1% → This is higher than best-practice and worth addressing now.
At 2%+ → Klaviyo and ISPs start treating it as a warning sign, which can lead to inbox placement issues if left unchecked.
For high bounce rates:
Implement double opt-in or a real-time validation tool right away.
Monitor closely and clean your list regularly.
Use segmentation tips from Part 1 and bounce handling instructions from Part 2 of this email series to protect deliverability.
Or book a call if you’d rather hand it off
In the next issue, we’ll cover how to tighten flow entry criteria for more control—so you can segment within flows and avoid sending to low-quality or unengaged contacts.
Talk soon,
xx Judith
Using Klaviyo yet? It’s built for smarter segmentation and better inboxing. → Try it now
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