ESP migration
Most platform switches go wrong in the same two places: sender reputation resets to zero because nobody warmed the new infrastructure, and order history gets left behind, which delays predictive analytics by six months. We run migrations between Klaviyo, Omnisend, Customer.io, ActiveCampaign, Brevo, and Mailchimp with both problems designed out.
Why do migrations damage deliverability?
Gmail and Yahoo score the sending domain and infrastructure, and a new ESP means new infrastructure with no history. Move your full volume on day one and the mailbox providers treat it like a cold sender, exactly the situation the February 2024 bulk-sender rules were built to police. Our warm-up schedule ramps volume over two to four weeks, most-engaged segments first, with SPF, DKIM, and DMARC re-verified on the new platform before the first send and Google Postmaster Tools watched daily through the transition.
What moves, in what order?
| Phase | What happens | Why the order matters |
|---|---|---|
| 1. Foundation | Authentication (SPF/DKIM/DMARC), domain setup, order-history import | History unlocks Klaviyo's predictive models (500+ customers, 180 days) without waiting |
| 2. Rebuild | Flows recreated and improved, signup sources re-pointed, segments rebuilt | A migration is the cheapest moment to fix flow architecture you already know is dated |
| 3. Warm-up | 2–4 week volume ramp on engaged segments, both platforms running | Reputation builds before full volume arrives; the old ESP covers the remainder |
| 4. Cutover | Full volume shifts, old platform enters read-only retention | One dated, reversible switch instead of a slow leak across two systems |
When is migrating the wrong call?
Often enough that we check first. If the real problem is list quality or flow architecture, the same problems arrive at the new platform with shipping costs on top. The audit sprint makes that call with data: when a Mailchimp account's complaint rate sits at 0.3% because 71% of sends target long-dead segments, suppression fixes it on the platform you already pay for. We take the migration work only when the platform is genuinely the constraint, usually because a brand needs the predictive layer covered inAI audience analysis.
How long does an ESP migration take?
Six to ten weeks for most accounts, driven by flow count and integration complexity rather than list size. The list itself moves in an afternoon; rebuilding fifteen flows, re-pointing signup sources, and running the parallel-send validation is what takes the calendar time. We publish the cutover date in week one and hold to it.
Will deliverability suffer after switching platforms?
It will if you move volume abruptly, because the new sending infrastructure has no reputation history with Gmail and Yahoo. We warm the new domain and IPs over two to four weeks, starting with your most engaged segments, while monitoring Google Postmaster Tools daily. Handled this way, placement typically holds through the transition.
Do we lose our engagement history and predictive data?
Order history migrates, and that is what predictive models feed on. Klaviyo needs 500+ customers with orders and 180 days of history before predictions unlock, so we import historical orders during setup rather than starting the clock from zero. Engagement events (opens, clicks) generally do not transfer; models recover within one to two months.
Which platforms do you migrate between?
Any pairing among Klaviyo, Omnisend, Customer.io, ActiveCampaign, Brevo, and Mailchimp, in either direction. The most common route we run is Mailchimp to Klaviyo for ecommerce brands that have outgrown campaign-only sending and want the predictive layer. The audit sprint tells you whether a migration is even worth it; sometimes it is not.
Thinking about switching?
Bring the reasons to a working session. We will either scope the migration or show you the cheaper fix on your current platform.
Book a working session