Switching Email Providers? Clean Your List First

Moving to a new email service provider feels like a fresh start, and in one way it is: the new sending infrastructure has no history with your subscribers. That is also the risk. A big first send with unchecked addresses is the fastest way to teach mailbox providers that you are not trustworthy, and you do it with a sender account that has no credit yet.

Why migrations are risky

• No reputation yet. Mailbox providers judge new sending domains and IPs by their first messages. A high bounce rate in week one stays on your record.
• Old problems travel with the file. Dead addresses, spam traps and complainers are in your export. They come along unless you remove them.
• Provider limits. Many services review new accounts. A first import with many invalid addresses can lead to a review or a pause before a single campaign is sent.

What to prepare before you export

1. Take the suppression data with you

Your old provider holds lists of people who unsubscribed, complained or hard-bounced. Export them and import them into the new service first. This is both good practice and, in many places, a legal duty: someone who opted out must stay opted out after you move.

2. Keep the consent record

For each subscriber keep the source and the date they signed up. If a person asks how you got their address, you need to answer.

3. Decide who is worth moving

You do not have to import everyone. A common split:

• Engaged recently (opened or clicked in the last six months): import first.
• Quiet for six to twelve months: import later, in a small batch, with a re-engagement message.
• Silent for over a year: leave behind or archive.

Verify before you import

Run the list you plan to move through bulk verification. Remove the invalid and disposable addresses. Look at the accept-all group: those are often corporate domains and are fine to import, but send to them in the second wave, not the first. Re-check the unknowns once; many resolve on a second try.

Verify the full list once rather than in several pieces over several weeks. Addresses go stale, and what was valid when you started may not be valid at the end of a month-long project.

Ramp up gradually

1. Week one: send only to your most engaged group, in small batches.
2. Weeks two and three: double the volume if bounces stay low and replies look normal.
3. Week four onwards: add the quieter groups.

If you also change your sending domain, authenticate it properly (SPF, DKIM and DMARC) before the first campaign. A new domain with broken authentication will not reach the inbox regardless of how clean the list is.

A short checklist

• Suppression and unsubscribe lists exported and imported
• Consent source and date kept for every record
• List split by engagement
• Verification done on the list you will import
• Domain authentication set up on the new service
• First sends small and to engaged subscribers only

You can try the verification step on a small part of your list with the free credits of a new account. For the full list, pick a credit pack; unused credits stay valid for 12 months, so the same pack can cover your next clean-up too.