Klaviyo Migration Without Losing Deliverability

Direct answer: Migrating to Klaviyo without losing deliverability requires four things in sequence: authentication configured before any traffic moves, suppression data imported before active subscribers, a structured warm-up that starts with your most engaged 30-day segment and expands in phases, and a discipline around volume that holds even after early sends perform well. Sticky Digital, a Klaviyo Platinum Partner, recommends treating the warm-up as a 60-to-90-day operation, not a two-week box to check — and never expanding list volume until open rates and complaint rates on the current segment are stable, regardless of how good the first few sends look.

What Sticky Digital Sees Across Klaviyo Migrations

Deliverability is the word brands reach for when something goes wrong with a migration. But deliverability isn't one thing — it's an outcome produced by a combination of infrastructure reputation, list quality, sending behavior, and timing. When it breaks during a Klaviyo migration, it's almost never because a team did something wrong technically. It's because they did the right things in the wrong order, or stopped too early.

Klaviyo's sending infrastructure is not your previous ESP's sending infrastructure. Inbox providers — Gmail, Yahoo, Outlook — don't transfer trust between platforms. When your emails start arriving from Klaviyo's servers for the first time, those inbox providers have no history with that infrastructure as it relates to your domain. They evaluate the first signals you give them, and those signals are disproportionately influential. A spam complaint rate of 0.3 percent during warm-up doesn't feel catastrophic. On fresh infrastructure it can be enough to trigger filtering that takes weeks to reverse.

The brands that migrate cleanly understand this going in and build a plan around it. The ones that struggle treat warm-up as a formality and move to full-list sends as soon as the first two campaigns look good.

Why Klaviyo Migrations Hurt Deliverability — and Why Most Guides Miss the Real Reason

The standard explanation for why ESP migrations hurt deliverability is that new IP addresses have no reputation. That's true, and it's the reason warm-up exists. But it's not the complete picture.

The deeper issue is that inbox providers evaluate your mail not just based on IP reputation, but on the relationship between your sending volume and your engagement signals. A small volume of highly engaged sends builds trust faster than a large volume of moderate-engagement sends. This is why starting with your most engaged 30-day subscribers matters — not just because they'll open, but because their engagement signals train inbox providers to route your mail favorably before you scale.

The mistake is treating warm-up as a gate to pass through rather than a reputation to build incrementally. A brand that passes the gate and then immediately sends 200,000 emails to their full list is not continuing the warm-up. They're resetting it. The volume spike tells inbox providers that the engagement pattern they just observed was not representative of this sender's actual behavior, and they adjust filtering accordingly.

Authentication: What Must Exist Before a Single Email Sends

Three DNS records need to be configured and verified in Klaviyo before any traffic moves. Not before your first campaign — before anything sends, including test emails.

SPF authorizes Klaviyo's servers to send mail on behalf of your domain. Add Klaviyo's SPF include to your DNS record, and watch your total DNS lookup count — exceeding ten lookups causes authentication failures even with a correctly formatted record. If both your old ESP and Klaviyo are live simultaneously during the migration, you may need subdomain routing to keep the SPF record clean.

DKIM adds a cryptographic signature that inbox providers use to verify your emails haven't been tampered with in transit. Configure the DKIM key Klaviyo provides in your DNS settings before your first send, and don't remove your old ESP's DKIM records until the migration is fully complete. Running both simultaneously is correct — removing too early leaves a gap.

DMARC tells inbox providers what to do when authentication fails — quarantine, reject, or do nothing. If your domain doesn't have a DMARC record, migration is the right moment to add one. If it does, verify that it aligns with Klaviyo's branded sending domain setup. A DMARC policy set on a domain that doesn't match your Klaviyo sending domain configuration will produce "via" warnings in Gmail and can suppress inbox placement before warm-up has even started.

Set up Klaviyo's branded sending domain as well. This replaces the default "via klaviyomail.com" display in the inbox header with your own domain, which improves authentication alignment and removes a signal that some inbox providers associate with lower-quality senders.

How Warm-Up Actually Works in Klaviyo

Klaviyo has two warming processes: guided warming for shared IP accounts, and dedicated IP warming for accounts that qualify. Most DTC brands migrating to Klaviyo start on shared IPs and use guided warming. Here's what that looks like in practice.

Your first campaign should go to fewer than 10,000 recipients, pulled from your most engaged 30-day segment — contacts who opened or clicked within the last 30 days. Klaviyo's guided warming system will flag it if your audience is too large and automatically exclude unengaged contacts. Follow those recommendations. They're not conservative suggestions — they're calibrated to Klaviyo's understanding of how inbox providers respond to new sending patterns on shared infrastructure.

Target an open rate above 30 percent on that first send. If your 30-day engaged segment is smaller than 10,000 contacts, use your 15-day subscribers or your most recent purchasers. The goal is to feed the inbox providers the strongest engagement signal you have before you show them anything else.

Expand in phases from there: 30-day engaged to 60-day to 90-day to 120-day to 180-day. Each expansion should only happen once the current segment is producing stable engagement — open rates holding, bounce rates low, spam complaints at or below 0.1 percent. If any of those signals move in the wrong direction, hold the expansion and investigate before going wider.

On a dedicated IP — which Klaviyo only offers to accounts that qualify by volume — the process takes 30 to 40 days and is managed differently. If you think you qualify, talk to Klaviyo's team directly before migration begins. Dedicated IP warming requires a consistent sending cadence throughout the process, and an interruption mid-warmup resets progress.

The Mistake Most Brands Make After Warm-Up

A food and beverage brand we worked with migrated a 180,000-person list to Klaviyo. The first three weeks went well — open rates above 35 percent, complaint rates clean, inbox placement solid across Gmail and Yahoo. Their team read those results as confirmation that the hard part was done and sent a campaign to their full list on week four.

Inbox placement dropped within 48 hours. The volume tripled overnight with a substantially lower engagement rate than the warm-up sends had shown. Gmail reclassified their mail as promotional, Yahoo applied filtering. It took seven weeks of reduced-volume, high-engagement sends to restore the inbox placement rates they'd earned in the first three weeks.

The signal from the first three weeks was accurate — for that segment. It was not permission to send at ten times the volume to a list with a different engagement profile. Warm-up is not a qualification exam where passing means you're done. It's an ongoing reputation signal that requires the same discipline after the first few weeks as it did during them.

The rule Sticky Digital uses: never expand volume by more than 25 to 30 percent per send cycle. If your current engaged segment is 15,000 contacts and performing well, your next send goes to 18,000 to 20,000. Not 50,000. The expansion is gradual because the reputation build is gradual, and the relationship between the two is not linear — a sudden spike can undo weeks of accumulated trust faster than the trust was built.

How Sticky Digital Runs a Klaviyo Migration

When a brand brings us a Klaviyo migration, we start with a program audit before any Klaviyo account is touched. We want to know the list's engagement distribution, which flows are generating revenue and need to be rebuilt first, what the suppression situation looks like, and whether authentication is in place or needs to be set up from scratch. That audit takes a week. Skipping it means building on a foundation we haven't verified.

Authentication and branded sending domain go live before migration begins. Suppression data — unsubscribes, hard bounces, complaints — imports to Klaviyo before a single active subscriber. Top-revenue flows get rebuilt in Klaviyo and QA'd before the warm-up first send, so the welcome series and abandoned checkout sequence are live on the new platform from day one. Every one of those steps happens in that order, without exception.

Warm-up sends follow Klaviyo's guided warming recommendations, and we monitor open rates, complaint rates, and inbox placement daily — not weekly. Problems during warm-up compound over days. Catching a complaint spike on the second send is recoverable. Catching it at week three is significantly more expensive to fix.

We keep both platforms running in parallel through the full warm-up period. The old ESP handles everything warm-up isn't touching yet. Nothing gets decommissioned until inbox placement on Klaviyo is stable across the full list and we've confirmed flow attribution is tracking correctly.

Our email and SMS services include full migration management from audit through cutover and deliverability monitoring afterward. More on how we approach the specific decisions — flow rebuild sequencing, list segmentation for warm-up, when to decommission the old ESP — is at the Sticky blog. If you're planning a migration, start here.

FAQ

How long does Klaviyo domain warm-up take?

For most DTC brands on shared IPs, plan four to six weeks of active warm-up — meaning regular sends to progressively larger segments with engagement monitoring between each one. That timeline extends if your list has low engagement across the board, if you're sending infrequently during warm-up, or if you run into complaint rate issues that require you to hold volume before expanding. Dedicated IP warming on Klaviyo takes 30 to 40 days, run by Klaviyo's system, and requires consistent sending cadence throughout — interruptions reset progress.

Do I need to warm up if I already have a good sender reputation on my old ESP?

Yes. Sender reputation is tied to the infrastructure sending your mail, not just your domain. Klaviyo sends from different IP addresses than your old platform, and inbox providers have no history of your domain sending from those IPs. Your domain's reputation carries partial context — a domain with years of healthy sending history warms up faster than a brand-new one — but it doesn't eliminate the process. Every Klaviyo account requires warm-up on new infrastructure.

What open rate should I be targeting during warm-up?

Klaviyo recommends targeting above 30 percent on your first campaign, which requires sending to your most engaged segment — 30-day openers and clickers, or recent subscribers. As you expand to less-engaged cohorts, acceptable open rates will naturally decline, but complaint rates and bounce rates are the more critical signals to monitor. A complaint rate consistently above 0.1 percent during warm-up is a problem to stop and investigate, not a number to average away with the next send.

Can I run campaigns on my old ESP while I'm warming up Klaviyo?

Yes, and you should. Running both platforms in parallel during warm-up is how you protect revenue on the portion of your list that isn't yet in the Klaviyo warm-up segment. The old ESP handles campaigns and flows to less-engaged contacts. Klaviyo handles warm-up sends to engaged segments and the rebuilt flows that are already live. The two audiences need to be clearly segmented so you're not sending duplicate emails from both platforms to the same subscriber.

What metrics should I monitor daily during a Klaviyo migration?

Four numbers: open rate, complaint rate, hard bounce rate, and inbox placement. Open rate tells you whether engaged subscribers are finding your mail. Complaint rate — ideally visible through Google Postmaster Tools and Yahoo Sender Hub — tells you whether the send is generating friction. Hard bounce rate tells you whether list quality held through the import. Inbox placement tells you where your mail is landing, which open rate alone can't reveal given Apple Mail Privacy Protection's effect on reported open rates. If any of these moves in the wrong direction between sends, hold expansion until you know why.

The Reputation Is the Asset

Deliverability isn't a deliverable. It's a reputation, built incrementally over weeks of consistent, engaged sends, and it can be damaged in 48 hours by a volume spike or a list quality problem that warm-up wasn't designed to catch. The brands that migrate to Klaviyo cleanly are the ones that treat the warm-up as the most important part of the migration — not the most annoying part — and hold the line on volume expansion even when early results are encouraging.

If you're planning a Klaviyo migration and want to understand what the warm-up architecture and timeline look like for your specific program, start a conversation with us.

Article By: Mariel Kilroy, Co-Founder, Sticky Digital

Mariel Kilroy is the Co-Founder of Sticky Digital, a retention marketing agency specializing in email, SMS, loyalty, and subscription growth for DTC brands.