- The single biggest Klaviyo deliverability move is setting up a branded (dedicated) sending domain instead of sending from Klaviyo's shared domain, which aligns your root domain, sending domain, and from-address.
- Most Klaviyo accounts have SPF, DKIM, and DMARC technically correct, which is exactly why senders wrongly assume infrastructure cannot be the problem; the real issues are usually domain setup, engagement, and warming.
- Klaviyo's per-send and per-flow reporting lets you trace a deliverability drop to the exact campaign, flow, or segment that caused it, rather than staring at a blended monthly average.
- Engagement-based segmentation and a sunset flow are the core ongoing levers: mailing chronic non-openers teaches providers your mail is unwanted.
- Any new dedicated domain or IP on Klaviyo must be warmed gradually; Klaviyo's Guided Warming keeps reputation steady when volume spikes around launches.
Klaviyo is one of the most powerful platforms in ecommerce email, and brands on it routinely cite strong returns, but only on the mail that actually reaches the inbox. The frustrating pattern that brings Klaviyo users to a deliverability guide is almost always the same: authentication is set up, the account looks technically correct, and yet open rates sag and campaigns quietly land in spam. The reason is that inbox placement on Klaviyo is decided by factors beyond the authentication checkboxes, and this guide walks through what actually moves the needle.
We will cover the setup decision that matters most (a branded sending domain), why technically correct accounts still fail, how to use Klaviyo's reporting to diagnose problems precisely, and the ongoing engagement and warming practices that keep your mail landing in the primary inbox rather than the promotions tab or spam.
The Setup That Matters Most: A Branded Sending Domain
If you take one action from this guide, make it this. By default, Klaviyo can send from a shared sending domain, meaning your mail goes out under a Klaviyo-owned domain shared with other senders. Klaviyo itself advises all customers to set up a branded (dedicated) sending domain, and for good reason: it aligns your root domain, your sending domain, and your friendly from-address, and that alignment is central to how mailbox providers judge your trustworthiness.
A branded sending domain means providers like Gmail, Outlook, and Apple Mail evaluate your mail on your own domain reputation, which you control and build over time, rather than on a shared domain whose reputation is influenced by other senders you cannot control. It also lets you properly implement and align SPF, DKIM, and DMARC on your own domain. Sending from the default shared domain, especially the unaligned scenario where your from-address domain does not match the sending domain, can read as a spoofing risk to filters and even get internal mail blocked.
Choosing your sending subdomain
When you set up a branded sending domain in Klaviyo, you choose a subdomain (for example, a prefix on your main domain used for marketing sends). This is also where the broader reputation isolation question comes in: using a dedicated marketing subdomain keeps your promotional sending reputation separate from your primary corporate domain, so a rough patch on marketing mail does not bleed into your transactional or business email. Pick a sensible subdomain and use it consistently.
Why Technically Correct Accounts Still Land in Spam
Here is the trap that catches experienced Klaviyo users. You check your authentication, confirm SPF, DKIM, and DMARC are all green, and conclude that infrastructure cannot be your problem. Most Klaviyo accounts are indeed technically correct on authentication, which is precisely why people rule it out and get stuck. But authentication being correct is table stakes, not a guarantee. The real culprits usually lie elsewhere:
- Still on the shared domain. Correct SPF and DKIM on a shared sending domain still means you inherit shared reputation. The fix is the branded domain above.
- Click-tracking domain reputation. Providers evaluate every domain in your message, not just the from-address. Default Klaviyo click-tracking links use a Klaviyo domain; setting up dedicated (branded) click tracking so links use your own domain removes a weak point that has nothing to do with content quality.
- Engagement decay. Mailing unengaged subscribers is the most common hidden cause. Providers watch who opens and who ignores you; sending to chronic non-openers tells them your mail is unwanted regardless of perfect authentication.
- Sending to a stale or unverified list. High bounce rates and spam trap hits from an unclean list damage reputation fast. Verify and clean before sending.
Green authentication checkmarks are a floor, not a finish line: The most dangerous belief in Klaviyo deliverability is my authentication is set up, so my infrastructure is fine. Authentication being correct simply means you cleared the entry gate. Whether you reach the inbox is then decided by domain reputation, click-tracking domain, engagement, and list quality. If you are in spam with perfect SPF and DKIM, stop re-checking authentication and start looking at your domain setup and engagement.
Use Klaviyo's Reporting to Diagnose Precisely
One of Klaviyo's real advantages is granular reporting, and it is underused for deliverability diagnosis. Instead of staring at a blended monthly delivery number, Klaviyo breaks delivery and engagement signals out per campaign and per flow. This lets you trace a deliverability drop to the specific campaign, flow, or audience segment that caused it.
Practically, this means when placement dips, you can ask precise questions: Is it one flow mailing an old segment? A specific campaign to a re-engaged group that soured? A particular audience with high complaints? Klaviyo also surfaces performance by inbox provider, so you can spot a problem concentrated at Gmail or Outlook rather than assuming a uniform issue. Diagnosing at the flow and segment level turns a vague deliverability is down into a specific, fixable cause.
Engagement-Based Segmentation and the Sunset Flow
The core ongoing lever for Klaviyo deliverability is disciplined, engagement-based sending. Because mailbox providers judge you heavily on how recipients interact with your mail, who you send to matters as much as what you send.
Segment by engagement recency
Use Klaviyo's segmentation to isolate profiles by engagement recency (for example, opened or clicked in the last 30, 60, or 90 days) and prioritize your most engaged subscribers, especially when sending volume is high or when warming. Mailing your engaged core consistently teaches providers your mail is wanted; blasting your entire list including long-dead contacts teaches them the opposite.
Build a sunset flow
A sunset flow automatically identifies chronically unengaged subscribers, gives them a final re-engagement attempt, and then suppresses those who still do not respond. This is one of the most important automations you can build in Klaviyo, because it continuously removes the dead weight that drags down your engagement metrics. Combined with a re-engagement series, it phases out non-openers so your list keeps teaching providers the right lesson. Pair this with pre-send verification and ongoing list hygiene to keep bounces and complaints low.
Warming New Infrastructure
Any time you move to new dedicated infrastructure, a newly registered sending domain or a new dedicated IP, you must warm it. Sending high volume from cold infrastructure is a classic way to trigger filtering, because providers see sudden volume from an unproven source and treat it as suspicious. Klaviyo offers Guided Warming, which gradually ramps your sending and helps keep reputation steady when volume spikes, such as around a product launch or a peak season like Black Friday.
The warming principle is the same as anywhere: start with your most engaged subscribers, increase volume gradually over days and weeks, and monitor closely. If you send infrequently and then need a big campaign, warm up beforehand by sending to your most engaged recent subscribers first rather than hitting your full list cold. Rushing volume on a fresh domain is one of the fastest ways to undo all your other good setup.
If your Klaviyo deliverability has already slipped, do not try to fix it with one big cleanup send to your whole list. Reputation recovers through consistent good behavior over time, not overnight, and blasting everyone (including the unengaged contacts that caused the problem) makes it worse. Instead, shrink your sending to only your most engaged segment (opened or clicked in the last 30 to 60 days), send them consistent, relevant mail for a few weeks to rebuild positive signals, and only then gradually widen your audience. You are re-teaching Gmail and Outlook that your mail is wanted, and that lesson takes repetition.
The Bottom Line
Klaviyo gives you excellent tools, but it does not make deliverability automatic. The brands that consistently reach the inbox on Klaviyo do four things: they send from a branded sending domain with aligned authentication and dedicated click tracking, they stop assuming green authentication checkmarks mean they are safe, they use Klaviyo's per-flow and per-segment reporting to diagnose problems precisely, and they mail based on engagement with a sunset flow removing the dead weight. Add disciplined warming for any new infrastructure, fold it all into an ongoing deliverability practice, and Klaviyo's power translates into inbox placement rather than spam-folder frustration.
Frequently Asked Questions
Usually not because of authentication, which most Klaviyo accounts have set up correctly, but because of domain setup, engagement, or list quality. The most common causes are still sending from Klaviyo's shared domain instead of a branded one, mailing chronically unengaged subscribers, using the default Klaviyo click-tracking domain, or sending to a stale, unverified list. If your SPF and DKIM are green but you are in spam, stop re-checking authentication and look at your branded domain setup and engagement-based segmentation.
Yes. Klaviyo advises all customers to set up a branded (dedicated) sending domain, and it is the single highest-impact deliverability action on the platform. It aligns your root domain, sending domain, and from-address, so mailbox providers judge you on your own domain reputation, which you control and build over time, rather than on a shared Klaviyo domain influenced by other senders. It also lets you properly align SPF, DKIM, and DMARC and set up dedicated click tracking on your own domain.
A sunset flow is an automation that identifies chronically unengaged subscribers, gives them a final re-engagement attempt, and suppresses those who still do not respond. It matters because mailbox providers judge you heavily on engagement, and continuing to mail people who never open tells them your mail is unwanted, which drags down inbox placement for your whole list. The sunset flow continuously removes that dead weight so your list keeps teaching providers that your mail is wanted.
Any new dedicated domain or IP must be warmed gradually, and Klaviyo offers Guided Warming to ramp your sending automatically. The principle is to start with your most engaged subscribers, increase volume gradually over days and weeks, and monitor closely, rather than hitting your full list at once from cold infrastructure. If you send infrequently and then need a large campaign, warm up first by mailing your most engaged recent subscribers. Rushing volume on a fresh domain is a fast way to trigger filtering.
Use Klaviyo's per-campaign and per-flow reporting rather than a blended monthly average. Klaviyo breaks delivery and engagement metrics out by individual campaign, flow, and audience, and surfaces performance by inbox provider, so you can trace a drop to the exact campaign, flow, or segment that caused it and spot whether a problem is concentrated at one provider like Gmail or Outlook. Pair this with an external reputation check and monitoring to see how your domain looks from the provider side.