Migrating from Dotmailer to Klaviyo: what to protect

The short answer

A Dotmailer-to-Klaviyo migration succeeds on three protections: every suppression record travels with the list, the sending domain's reputation carries across deliberately, and the two platforms hand over on a hard cutover date with neither sending into the gap. The runbook below orders the work so each protection is in place before the step that needs it.

The migration runbook

The move from Dotmailer, now trading as Dotdigital, to Klaviyo follows a predictable sequence, and the order is the protection.

1. Export everything from Dotmailer: the contact list, every suppression record (unsubscribes, hard bounces, complaints), custom data fields, and the engagement history that will define your engaged segments on day one.
2. Import to Klaviyo with suppressed contacts arriving marked as suppressed, and spot-check by searching known unsubscribers before anything else happens.
3. Map the custom fields and rebuild the segments that sending policy depends on, engagement windows first.
4. Rebuild the flows in priority order: welcome, abandoned cart and post-purchase live and tested before cutover, since these earn from day one, with the long tail of automations following after.
5. Set up and verify the branded sending domain and authentication, per the authentication guide.
6. Cut over on a named date: Dotmailer flows paused, Klaviyo flows live, campaigns switching platform the same week.

Suppressions: the step that matters most

Klaviyo has no way of knowing who should stay suppressed unless they arrive in the import marked that way, and Klaviyo's own migration guidance is explicit that unsubscribe and bounce history should come across alongside the opt-ins. Sending to contacts who unsubscribed or complained on the old platform is a compliance and deliverability risk in one, and it is the classic migration failure: the fresh platform cheerfully mails years of accumulated opt-outs, complaints spike, and the new setup starts life with a reputation problem it inherited from a spreadsheet.

Treat the suppression export as the deliverable to verify hardest. Count the suppressed records on both platforms after import, and reconcile any difference before the first send rather than after the first complaint.

Protecting sender reputation through the transition

During the migration period both platforms exist side by side. Dotmailer keeps sending flows and campaigns until the cutover date, and Klaviyo sends nothing until it is ready. The risk is contacts hearing from both platforms at once, or hearing from neither because flows went live in Klaviyo before the Dotmailer flows were paused, and a clear cutover date with a short buffer where neither platform sends is the cleanest way through.

Reputation is attached to the sending domain, so a brand that carries its established domain across brings its history with it, and Klaviyo's guidance confirms an established domain with real sending history does not restart from zero. A brand setting up a fresh sending subdomain is starting that subdomain from nothing, and it should be warmed properly, beginning with the subscribers who already open and widening as the results hold. Either way, the first weeks on the new platform are the wrong time to email the whole list.

The first thirty days on Klaviyo

The migration ends when the evidence says the new platform performs, not when the import finishes. Watch four things across the first month: deliverability metrics against the Dotmailer baseline you recorded before the move, flow revenue recovering to its previous run rate as the rebuilt automations bed in, any suppression complaints or unsubscribes from contacts who should never have been mailed, and the data joins, since a mis-mapped field shows up here as a broken personalisation or a mis-firing segment.

Keep the Dotmailer account readable for a quarter even after sending stops, because the historical reporting and the original consent records answer questions that will come up, and closing it on cutover day saves little and costs the audit trail.

Questions we hear about the migration