Every email platform promises a one-click import. What they do not mention is that the import is the easy part — and it is not where migrations go wrong.
Warm the new domain first
If you are changing sending domains, start two weeks before the migration. Send to your most engaged segment only, in rising volume. Moving 40,000 addresses to a cold domain on day one is how you land in spam and stay there.
Export more than the addresses
A CSV of emails is not your list. Export, at minimum:
- Subscribe date and source — you need these for consent records
- Engagement history, or at least a last-opened date
- Tags, segments, and custom fields
- Unsubscribes and bounces
That last one matters most. Import a clean list without your suppression data and you will email people who already opted out, which is both a legal problem and a deliverability one.
Rebuild automations before you cut over
Sequences never port cleanly. Rebuild them in the new platform, run them against a test segment, and only then point your forms at the new provider.
Keep the old account for 30 days
Not paused — active. You will discover a form, a Zap, or a checkout hook still pointing at the old system, and you want those subscribers landing somewhere real while you fix it.
Then, and only then, migrate
Import in engagement order: most engaged first, dormant last. If deliverability degrades, you will see it in the first batch, while it is still recoverable.