The short answer

Treat the move like a small data migration, not a copy-and-paste job. Export and preserve every contact status, map your fields and tags before importing, rebuild automations while the old account is still open, and test with a tiny internal group before sending to subscribers.

Most migration trouble comes from moving email addresses but forgetting the history attached to them.

Make a complete backup first

Download everything the old provider will give you: active subscribers, unsubscribed contacts, bounced or cleaned addresses, tags, groups, custom fields, signup dates and sources, consent records, campaign reports, templates, and automation maps.

Keep the original export untouched. Make a working copy for cleanup. Mailchimp's export guidance, for example, says its full audience export separates subscribed, unsubscribed, non-subscribed, and cleaned contacts. Your provider may package the data differently, so read its export documentation before closing anything.

Unsubscribed and suppressed people matter even though you won't market to them. They help stop an old opt-out from becoming an accidental new subscription after the move.

Build a field map before importing

Create a simple table with four columns: old field, example value, new field, and action needed. Map obvious information such as first name, then tackle the fields that control behavior:

• subscription status.
• signup source and date.
• consent wording or version.
• interests, tags, and groups.
• customer status and purchases.
• automation entry and completion status.

Don't assume the same word means the same thing in both systems. One provider's “group” may behave like another provider's “tag.” If a status cannot be imported, preserve it in your backup and ask the new provider how its suppression system works.

Move in a controlled order

First authenticate your sending domain in the new account. Next create fields and tags, import suppressed contacts according to the new provider's instructions, and then import valid subscribers. Rebuild forms, integrations, templates, and automations. Pause live triggers until your tests are finished.

Use a test group containing addresses you control at several mailbox providers. Submit every form, follow every branch, click every link, unsubscribe one test address, and confirm that it stays suppressed. Compare counts by status and tag before and after the move.

For the first live send, use a recent, engaged segment rather than the entire database. Watch bounces, complaints, unsubscribes, and replies. Keep the old account read-only for a short overlap period if your plan and privacy obligations allow it.

Protect the permission, not only the file

Consent and recordkeeping requirements vary by location. The UK's Information Commissioner's Office advises recording when and how consent was obtained and what messages it covers. Check the laws that apply to your business and subscribers, your contracts with both providers, and your own privacy notice. Get qualified advice when you are unsure.

Never mark an uncertain contact as subscribed just to make the import work. A smaller clean migration is safer than carrying a mystery list into a new system.

Sources and further reading

• Mailchimp: View or export your contacts
• UK Information Commissioner's Office: Using marketing lists

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Helpful WAHMN article

For a worked example and more help with this topic, read Kit vs. MailerLite for a New Online Business: Which Should You Start With?.

Related Questions

• When should a small business segment its email list, and when is one list enough?
• Why should I avoid buying an email list, even if the seller says the contacts opted in?
• What is email deliverability, and why are my marketing emails going to spam?
• Why are people unsubscribing from my email list, and which reasons should I actually worry about?

Related WAHMN resource

If email is an important part of your business, this system helps you build the setup, list, messages, and follow-up process around it. See Email Marketing System.