How do I migrate to Klaviyo without breaking deliverability, data, or flows?
Short answer: Migration strategies from other ESPs require proper sequencing of data, DNS, and flows. Common pitfalls break deliverability and cost revenue.
Most migrations don't fail loudly. They fail quietly: open rates dip, flows misfire, attribution breaks, revenue softens. By the time you notice, the damage is done. These are sequencing and strategy mistakes, not technical failures, that prevent you from building what actually drives performance post-migration: a clean data foundation, automation that works from day one, and personalization that reaches individual customers based on real behavior. Here's what to watch for—and how to set yourself up to use the platform the way it's designed to work.
I'm Ali, an eCommerce strategist and digital marketing leader at PeakActivity, as well as a Klaviyo Champion. My specific expertise as Chief Digital Officer is overseeing migration projects to ensure seamless transitions, reduce costs, and maximize returns for various industries. What follows are the patterns I see repeatedly and the fixes that actually work.
Here's the thing most teams miss: migration is a reset. A chance to clean up years of accumulated data debt, fix what wasn't working, and build something that actually reflects how your business operates today. The teams that treat migration as a checkbox exercise carry their old problems into a new platform and wonder why performance doesn't improve. The teams that treat it as a strategic reset come out the other side with a cleaner list, a stronger sender reputation, and a setup built for how Klaviyo actually works. The mistakes below are what separate those two outcomes. Each one comes back to the same principle: the platform works best when every customer interaction, purchase, and preference flows into a single profile. Migration is your chance to set that up correctly.
1. Skipping the plan and hoping for the best
The problem
New platform, fresh start. But excitement without a plan is just expensive chaos. I've seen migrations stall for weeks because nobody wrote down what needed to happen first—no phases, no owners, no sequencing. Just a login and a lot of enthusiasm.
What breaks
When there's no roadmap, sequencing breaks down. Flows get built before integrations are validated. DNS gets rushed. The cutover happens before anyone's confirmed the basics work. And by the time you realize steps were skipped, you're already troubleshooting in production.
What to do instead
Before you touch a single setting, write the plan. Every phase needs to be mapped: integrations, DNS, list import, flow builds, warmup, cutover, validation. Assign owners, set checkpoints, and hold the line on sequencing. The temptation is to start building while you're still figuring things out. Resist it. Winging it costs more than planning ever will.
2. Building before your data is ready
The problem
I get it—you want to make progress. So you start building flows while the integrations are still being set up. It feels like progress, but it's not.
What breaks
Everything in Klaviyo runs on event data—and the events only exist once your integrations are properly configured. If Viewed Product, Added to Cart, and Started Checkout aren't firing correctly from your Shopify integration, your abandoned cart flow is either targeting the wrong people or not triggering at all. You won't know until it's too late. Bad data in means bad logic out—and bad logic means your flows underperform from day one. Every flow and segment you build will pull from your customer profiles. If those profiles are missing event history because integrations weren't validated first, your targeting decisions are based on an incomplete picture.
What to do instead
Set up integrations first. Validate that key events are firing. Test across real scenarios before you build anything. The flows will go faster when the foundation is solid. Skipping ahead costs more time than it saves.
3. Importing contacts without knowing where they came from
The problem
This is the question most teams don't ask until someone makes them: how did these people opt in? When? Do you have proof? For a lot of lists that have been sitting in an ESP for years, the honest answer is "I'm not totally sure."
What breaks
Importing contacts without clear opt-in documentation creates legal exposure under GDPR, CAN-SPAM, and CASL—regulations that carry fines and can require you to purge entire lists. But before you even get to the legal risk, there's a deliverability one. People who don't recognize you—or who never properly opted in—mark you as spam. That reputation follows you to Klaviyo's infrastructure and can tank performance before you've sent your first real campaign.
What to do instead
Audit the list before it moves. Only import contacts with verified, documented opt-in. If provenance is murky on a segment of your list, suppress them or run a re-permissioning campaign first—a targeted email to your old list asking subscribers to actively confirm they want to continue hearing from you. Yes, most won't respond. That's the point. A smaller, cleaner list will outperform a large questionable one every single time.
4. Migrating too much instead of less
The problem
The instinct is to bring everything over. Full list, all historical data, every tag and custom field—just in case. It feels like the safe move. It isn't.
What breaks
Importing a bloated, unfiltered list drives up costs immediately, hurts deliverability from the first send, and floods Klaviyo with years of messy data it can't use effectively. Historical engagement from another platform doesn't translate cleanly because open and click tracking differs between ESPs, and Klaviyo can't act on data it didn't collect. And if your profile attributes are inconsistently named or structured in your old ESP—which they almost always are—you're importing that chaos directly into a clean system.
What to do instead
Start with engaged contacts from the last 60–90 days. But before anything gets imported, do the data hygiene work. Normalize your profile attributes. Standardize naming conventions. Clean up custom fields. Decide what your data structure looks like in Klaviyo before you populate it—not after. Think of it like defining a schema before you fill a database. This should be in your migration plan from day one, not an afterthought on import day.
5. Not checking list settings before integrations go live
The problem
This one surprises people because Klaviyo's list settings aren't always configured the way you'd expect out of the box. Most teams don't think to check until something fires that wasn't supposed to.
What breaks
Here's the scenario: Double opt-in is enabled, you connect your Shopify integration, and suddenly contacts are getting a confirmation email nobody planned for. During a migration, when you're actively testing and connecting systems, that's the worst possible moment for an unintended send. Confused customers, an uptick in unsubscribes, and a support ticket you didn't budget for—before you're even fully live.
What to do instead
Check every list's settings before you connect a single integration. Know what's enabled, what will trigger, and under what conditions. If double opt-in is part of your compliance strategy, great—but make it a deliberate decision, not an accident. Five minutes of review prevents a very visible mistake.
6. Skipping IP warmup under pressure
The problem
The campaign calendar doesn't pause for your migration timeline, and someone in leadership always wants to know why you haven't sent anything yet. So warmup gets treated as optional. It isn't.
What breaks
Klaviyo runs on different infrastructure than your old ESP. Inbox providers don't have history with you yet. Send too fast and you're a new sender asking for trust you haven't earned. In my experience working with brands post-migration, teams that skip warmup routinely see a 15–30% performance drop in the first few weeks—and in worse cases, spam folder placement that takes weeks to dig out of.
What to do instead
Warmup is non-negotiable. Start with your most engaged subscribers—30-day openers first—and ramp to 60-day, then 90-day over 1–3 weeks. Watch complaints, bounces, and open rates the whole way. If you have access to Klaviyo's deliverability team, work directly with them on timing—they have platform-level visibility into what's happening with your sends that you don't have on your own. If you don't, follow Klaviyo's published warmup guidance closely and monitor your metrics daily.
7. DNS missteps that break authentication
The problem
DNS changes feel like a formality until they aren't. The mistake I see most: teams remove old ESP records too early, or rush through Klaviyo's setup without fully verifying before making changes.
What breaks
You might see authentication conflicts, DMARC failures, "via" warnings in the inbox (where recipients see your email is sent "via" another domain, signaling potential spam), and in bad cases, spam placement. Sometimes these don't show up until you're days into a live campaign and debugging DNS is the last thing you want to be doing.
What to do instead
Add and fully verify Klaviyo's DNS records—DKIM, SPF, branded sending domain—before you remove anything from your old ESP. Keep the old setup intact and authenticated through the full cutover window. The sequence is add new, verify new, confirm everything works, then remove old. In that order. Always.
8. Running two platforms without a real cutover plan
The problem
Both ESPs end up active at the same time—Klaviyo flows are live but nobody paused the old ones. Or the cutover happens without a documented plan for who owns what send on which day.
What breaks
Customers get duplicate emails. welcome flows fire twice. Abandoned cart sequences overlap. Complaint rates spike. And now you're doing customer service triage on top of a migration. Before you pull the plug on the old platform, you need to confirm Klaviyo flows are triggering correctly, events are firing, and revenue attribution is tracking. Cutting over before validating is how good migrations turn into expensive debugging sessions.
What to do instead
Pause all flows in the old ESP before activating them in Klaviyo. Use suppression lists and exclusion logic wherever overlap is possible. Set a specific cutover date and time. Document what moves when, and put one person in charge of the transition window. Assumptions are how things get missed.
9. Rebuilding everything exactly as-is
The problem
It feels efficient. You're not redesigning—just moving. Copy the segments, recreate the flows, mirror the conditions. Same logic, new platform. Except it isn't the same platform.
What breaks
A 1:1 rebuild carries over everything that wasn't working. Segmentation logic that made sense somewhere else. Flows built around workarounds Klaviyo doesn't need. Conditions nobody's reviewed in three years. You migrate the technical debt right alongside the templates.
What to do instead
Treat migration as an audit. Pull performance data on every flow and segment before you rebuild anything. Keep what's earning its place. Drop what isn't. Then build to the platform's native capabilities. Instead of recreating workaround logic, consider what you can now do directly: store customer preferences and use them in flows, let predictive models surface churn risk and high-value profiles automatically, and build segments that update based on real-time behavior rather than static lists. Migration is the time to ask which capabilities you couldn't fully use before—and which ones you can now build into your setup from day one.
10. Mistaking the stabilization period for failure
The problem
Metrics dip post-migration and someone panics. Open rates are down. Attribution looks off. Leadership starts asking questions. The instinct is to start making changes immediately.
What breaks
When you optimize before you have a stable baseline, you're just adding noise. You're changing variables before you know what's working. Teams that panic-optimize in the first two weeks after migration frequently make things measurably worse before they get better.
Take this example from a Klaviyo Community AMA, a sender described exactly this dilemma: sending to the full list hurt deliverability, but sending only to engaged subscribers meant no revenue. Klaviyo's response was unambiguous — prioritize the repair, treat it as a reset, and expand gradually once metrics stabilize.
Eddie Sun wrote:
Hi! I’d really appreciate your insight on this.
Our email deliverability score is currently quite low, and Klaviyo suggests we use AI repair plan to skip sending to users who haven’t interacted with us in the last 30 days. The issue is, if we follow that, we’re left with a very small segment to send to.
We’ve tried the AI repair plan before, and it actually did help improve our score at the time. But recently, our deliverability has dropped again, and I’m unsure what the best approach is going forward.
The dilemma is:
When we send to the full list, our deliverability takes a hit — but we consistently see sales.
When we only send to engaged subscribers, our deliverability improves — but we see no revenue.
Would you recommend using the AI repair plan again and focusing only on the engaged segment for a while, even if that means sacrificing short-term revenue? Or is there a smarter way to balance both deliverability and sales?
Thanks in advance!
Hello
@Eddie Sun ,Yes, i would recommend focusing on your engaged segment and gradually ramping up your volume.
Avoid doubling your volume from a week to the next, instead increase it by a maximum of 20% week over week.If you notice your metrics starting to drop, slow down and keep your volume stable for a longer period.
What to do instead
There is a normal 1–2 week stabilization period after migration. Expect it. In the first 48 hours, watch for hard errors—bounces, authentication failures, flows not triggering. Those need attention fast. But metric performance? Give it time to stabilize before you touch anything. The goal right after migration isn't improvement. It's confirmation that nothing is broken. That's what success looks like right after migration.
The bottom line
A good migration doesn't feel dramatic. It feels controlled. No major spikes, no major drops. Just steady performance while things transition cleanly from one platform to the other. That's the goal. If you're constantly troubleshooting, something went wrong earlier in the process.
Avoid these ten mistakes and you won't just get through the migration. You'll come out the other side with clean data flowing into unified customer profiles, a sender reputation built on engaged subscribers, and a setup where every flow, segment, and AI-powered feature draws from the same complete customer picture.
Plan it. Sequence it. Validate it. Then send. If you're early in your migration planning, start with Klaviyo's official migration guide to map out your phases—then come back to this list to audit your approach before you go live.
Let me know 👇
Which of these mistakes have you actually hit during a migration? Drop it in the comments and if you found a fix that isn't here, share it.
