Migrate from Mailchimp: what it takes and how to do it

Migrating an email tool is mostly an exercise in finding out what you were relying on that is not in the export. The contact list is the easy part and the part everybody plans for. The parts that hurt are the ones with no file format.

Done in the right order this is a two-week job with no interruption to sending. Done in the wrong order it is a deliverability incident.

What actually moves

• Contacts — email, name, merge fields, tags, subscription status. Exports cleanly as CSV, or through the API with more fidelity.
• Segments, as definitions you re-create rather than as data. Write them down before you cancel.
• Unsubscribes and cleaned addresses. These are the most important rows in the file. Export them separately and import them as suppressions first, before any other contact.
• Campaign history, as a record. Useful for reference, rarely worth importing.

What does not move

1. Consent provenance. Signup source and timestamp are partially available and often thin. Export whatever exists and keep the original files: an imperfect historical record you retained beats a perfect one you did not.
2. Automations. The logic, the timing, the exit conditions and the branching all have to be rebuilt by hand. Screenshot every one before you lose access.
3. Templates. HTML exports, but tool-specific merge tags, conditional blocks and the drag-and-drop structure do not survive.
4. Engagement history. Opens and clicks per contact are largely unavailable, which matters because your new engagement gate has nothing to filter on for the first months.
5. Sending reputation. This is not a file. If you are also changing sending domain or provider, you are starting from nothing, and that deserves its own plan.

The order to do it in

1. Set up authentication on the new sender — SPF, DKIM, DMARC — and verify with real test sends to each major mailbox provider.
2. Import suppressions before anything else. Unsubscribes, hard bounces, complaints. Getting this backwards means mailing people who opted out, which is both a complaint spike and a breach.
3. Import contacts with their consent data, however partial.
4. Rebuild segments, then compare counts against the old tool. Differences are informative and usually reveal a definition you had forgotten.
5. Rebuild flows, but leave them switched off.
6. Send one campaign from the new tool to your most engaged few thousand.
7. Switch flows over one at a time, cart recovery last — it is the one with revenue attached.

The fortnight where both are running

Keep the old tool live and paid for a fortnight past the switch. It costs one month's subscription and it buys you the ability to compare.

• Never have both sending the same flow. Switch one off as the other goes on, and check the old one is genuinely off rather than paused.
• Watch for duplicate sends from the receiving end — subscribe yourself with an address on each side.
• Compare revenue per recipient on the same campaign type, not open rates, which will not be comparable across tools anyway.

Cancel only after this list is clean

Before you cancel, take: the full contact export, the suppression export, screenshots of every automation, the HTML of every template you still use, a copy of your forms and their exact consent wording, and any DNS records pointing at the old provider.

Then remove the old provider's SPF include and DKIM records — leaving them behind is a live authorisation for a service you no longer control to send as you.