An example: you send to 40,000 subscribers. 6 months ago the open rate was 38%. This month it is 22%. The subject lines are as good as ever and email revenue is down.
The list did not stop caring. Many of the emails stopped arriving.
Deliverability is the share of your sends that reach the inbox. Google, Apple and Microsoft score every send you make. Your email platform does not do this for you.
3 things inbox providers check
| Check | The question | Where to look |
|---|---|---|
| Authentication | Does the email come from you? | SPF, DKIM and DMARC records on your sending domain |
| Sender reputation | How have people treated your mail before? | Spam rate in Google Postmaster Tools. Keep it below 0.1% |
| Engagement | Do people open and click? | Subscribers who have not opened in 6 months or more |
Authentication lives in 3 DNS records on your sending domain. This is what they look like (example, redrawn, not a screenshot):
Authentication is the easiest fix and the one most often skipped. Engagement is the most common cause of slow decline in a growing brand. A list full of cold subscribers tells providers your mail is unwanted.
Fix it in 3 moves
- Authenticate. Check SPF, DKIM and DMARC for your sending domain. In Klaviyo, set up a custom sending domain and do not rely on the shared one. Aim for DMARC at
p=quarantineorp=reject.p=noneis a starting point. - Segment and suppress. Send mostly to people who engaged in the last 90 days. Run one deliberate win-back to the 90 to 180 day inactives. Stop broadcasting to anyone with no engagement past 180 days.
- Lower the complaint rate. Keep spam complaints below 0.1%. Google’s email sender guidelines require every sender to keep the spam rate in Postmaster Tools below 0.3%. Above it, your mail is more likely to be filtered. Make unsubscribing easy: a buried link sends people to the spam button. If you send more than 5,000 emails a day to Gmail, the same guidelines require one-click unsubscribe on marketing emails, in force since February 2024.
Back to the example. Say 14,000 of the 40,000 have not opened in 6 months. Suppress them and send to the other 26,000. If 8,800 of them open (22% of 40,000), the open rate on the 26,000 is 34%. The number rises because the list is honest. More importantly, providers see people opening your mail again.
What Klaviyo does and does not do
Klaviyo’s deliverability dashboard shows bounce rate by campaign, unsubscribe trends and list growth against engagement. Check it weekly.
It cannot fix your domain reputation. That lives with inbox providers and builds over months of consistent sending to people who want the mail.
Why it compounds
Fewer inbox placements mean fewer opens, which tells providers your mail is unwanted, which means fewer inbox placements.
This week: check your authentication records, look at your spam complaint rate and suppress the unengaged before your next broadcast.
Related reading
- The automated emails and texts every ecommerce brand needs: the 5 flows that depend on inbox placement
- Klaviyo vs Mailchimp for ecommerce: what each platform handles for you
Free tool: First-Party Data Checklist. Clean data keeps emails out of spam. Work through 20 checks across collection, activation, measurement and privacy. Open the checklist
Quick answers
What is email deliverability?
Deliverability is the percentage of your emails that reach the inbox rather than spam or being blocked entirely. It's determined by technical authentication, sender reputation, list hygiene and engagement signals.
Why do my emails go to spam even with a clean list?
A clean list helps but isn't enough. Inbox providers look at authentication records (SPF, DKIM, DMARC), your sending IP's reputation, engagement rates and spam complaint rates. One weak signal can drag the rest down.
How does Klaviyo affect deliverability?
Klaviyo manages your sending infrastructure and provides deliverability monitoring, but your domain reputation is yours to build. Proper list hygiene, segmentation and authentication on your own domain are still needed.
How long does it take to repair poor deliverability?
Mild reputation issues can recover in 4 to 8 weeks with consistent sending to engaged segments only. Severe cases, spam complaints above 0.3% or a blacklisted IP, can take months and may require a domain migration.
What open rate tells me deliverability is a problem?
There's no single threshold, but a sudden unexplained drop in open rates, especially if click rates hold, often signals deliverability rather than content. Check your Klaviyo deliverability dashboard and run a seed test.
