Switching email platforms? Clean your list before you import
Moving from Mailchimp, Constant Contact or another email tool to a new one feels like a fresh start. It's also the moment lists most often go wrong. Unsubscribes get left behind, columns land in the wrong fields, and the first send from the new platform bounces off years of dead addresses.
Before you import into a new email platform, export everything, including unsubscribed, bounced and cleaned contacts, and import those as unsubscribed or suppressed. Match the columns, remove duplicates and check the addresses. Then start sending slowly, set up SPF and DKIM for the new platform, and keep the old account open until opt-outs from your last emails are handled.
This guide walks through the move in order: export everything, bring your suppressions with you, match the fields, remove duplicates, check the addresses, then start sending slowly with your sending domain set up properly. Every platform labels things a little differently, so check your new tool's help pages for its exact menu names.
Step 1: Export everything, not just your subscribers
Most people export their active subscribers and stop there. Export every group your old platform has, including the people you can't email:
- Subscribed contacts, the people you'll keep emailing.
- Unsubscribed contacts, the people who opted out.
- Bounced or cleaned contacts, addresses that failed in the past.
- Any complained, blocked or suppressed groups your platform keeps.
In Mailchimp, for example, exporting an audience gives you a ZIP file with separate CSV files for subscribed, unsubscribed, non-subscribed and cleaned contacts. Only account Owners and Admins can export, and each export stays in your account for 30 days. Other platforms work differently, so look for every contact status, not just "active".
Save an untouched copy of every file before you change anything. Do all your cleaning on a second copy.
| File in the export | Who's in it | What to do in the new platform |
|---|---|---|
| Subscribed | People who agreed to get your emails | Clean and check, then import as subscribed |
| Unsubscribed | People who opted out | Import as unsubscribed or suppressed. Never as subscribed |
| Cleaned (or bounced) | Addresses that bounced or were removed as undeliverable | Import as suppressed, or keep on your own do-not-send list |
| Non-subscribed | Contacts who never opted in to marketing, such as some customers | Only import as subscribed if you have their permission |
Step 2: Bring your unsubscribes and bounces with you
Your new platform has no idea who opted out of your old one. If you only import subscribers, it's easy for an old unsubscribe to slip back in through another spreadsheet or an old export. The first send from the new tool then goes to people who asked you to stop.
That's a legal problem as well as a reputation one. In the U.S., the FTC's CAN-SPAM guide says you must honor an opt-out within 10 business days, and once someone opts out you can't sell or transfer their address, except to a company you've hired to help you comply. It also says you can't contract away your responsibility if another company sends your email. Changing platforms doesn't reset anyone's opt-out.
- Import your unsubscribes as unsubscribed or suppressed in the new platform, not as regular contacts. Many tools have a specific option for this. Constant Contact, for example, has an "Add unsubscribed email addresses" import for lists from other providers, and Mailchimp lets you set an import's status to Unsubscribed.
- Treat old bounces the same way. They failed before. They'll almost certainly fail again.
- Keep your own master copy. A separate do-not-send list, with the reason and the date, protects you the next time you move. See what a suppression list is and why you keep it forever.
- Don't close the old account too early. The FTC guide says your opt-out method must keep working for at least 30 days after you send a message. Make sure unsubscribe requests from your last emails still reach you.
Step 3: Match the column fields
Your old export's column names won't match your new platform's fields exactly. Before you import, decide where each column should go:
| Old export column | New platform field | Watch out for |
|---|---|---|
Email Address | Stray spaces and capital letters | |
First Name, Last Name | First name, Last name | Names stuck together in one cell |
TAGS | Tags or lists | Several tags in one cell, separated by commas |
OPTIN_TIME | A custom "Signed up" field | Date format changing on the way in |
ZIP | Postal code | Leading zeros dropped by Excel (02134 becomes 2134) |
- Create custom fields first. If the new platform doesn't have a field for something you track, set it up before the import so the column has somewhere to go.
- Keep signup details. If your export has a signup date or source, bring it with you. It's your record of how people joined.
- Watch Excel. Opening a CSV in Excel can strip leading zeros from ZIP codes and change dates. See how to prepare a contacts CSV for import for how to avoid that.
- Test with a few rows first. Import 10 contacts, check that every field landed in the right place, then import the rest.
Step 4: Remove duplicates
If you're combining more than one audience, list or platform, the same person will often appear more than once, sometimes with different capital letters or a stray space. Remove the extra copies before you import.
- ListaFix's free duplicate remover does this in your browser, so your list stays on your computer.
- If the duplicates have different details, such as a phone number in one and a name in the other, merge them carefully. See how to merge two contact lists without losing anything.
- Unsubscribed always wins. If someone is subscribed in one file and unsubscribed in another, treat them as unsubscribed. Remove them from the subscribed import.
Step 5: Check the addresses before your first send
Your old platform may have been quietly removing bounces for years, but any list from a spreadsheet, an event or an old import can still be full of dead addresses. A new platform has no history with you, so a burst of bounces on your very first send is a bad start.
Check the subscribed file before you import it, or at least before you send. A checker that asks each mail server about the mailbox, without sending an email, finds the addresses that look fine but no longer work. If you want help deciding what to keep, our Mailchimp cleaning guide explains how to handle each kind of result.
Step 6: Start sending slowly
Mailbox providers judge new senders by how their mail is received. If you move to a new sending domain or a new dedicated IP address, they don't know you yet. Sending your whole list on day one can look like a spammer.
- Start with your most engaged contacts, the people who opened or clicked recently.
- Increase the volume gradually over several sends. Google's sender guidelines advise starting with a low volume to engaged users and increasing slowly, and warn against sudden spikes.
- Watch bounces and spam complaints after each send. If they rise, slow down.
- Ask your new platform how it handles this. Many send from shared IP addresses they manage themselves, while dedicated IPs usually need a warm-up plan. Either way, a gradual start helps.
Step 7: Set up SPF and DKIM for the new platform
SPF and DKIM are DNS records that prove your new platform is allowed to send email for your domain. Without them, more of your mail may land in spam or be rejected. Google, for example, requires every sender to Gmail to set up SPF or DKIM, and bulk senders to set up SPF, DKIM and DMARC.
- Your new platform will give you the records to add. Add them where your domain's DNS is managed, then use the platform's check or verify button.
- A domain should have only one SPF record. Add the new platform to your existing SPF record rather than creating a second one.
- Once you've fully moved, remove records for the old platform that you no longer use.
For plain-English explanations of SPF, DKIM, DMARC and keeping mail out of spam, see EmailNa's guide to SPF, DKIM and DMARC.
A moving checklist
- Export every contact status from the old platform and save untouched copies.
- Import unsubscribes and bounces into the new platform as unsubscribed or suppressed.
- Keep your own master do-not-send list.
- Match each column to a field, create custom fields, and test with 10 rows.
- Remove duplicates. Unsubscribed always wins.
- Check the addresses before the first send.
- Set up SPF and DKIM for the new platform.
- Start with engaged contacts and increase volume slowly.
- Keep the old account open until opt-outs from your last emails are handled.
This is general information, not legal advice. Mailchimp and Constant Contact are trademarks of their owners; EmailNa and Veml aren't affiliated with them.
Questions people ask
- Do I need to import unsubscribed contacts into my new email platform?
- Yes, as unsubscribed or suppressed contacts, not as subscribers. Otherwise an old opt-out can slip back onto your list, and emailing people who opted out goes against CAN-SPAM's opt-out rules in the U.S.
- What's in a Mailchimp audience export?
- Usually a ZIP file with separate CSV files for subscribed, unsubscribed, non-subscribed and cleaned contacts. Only account Owners and Admins can export, and each export stays available in your account for 30 days.
- Should I verify my list before moving to a new email platform?
- Yes. A new platform has no history with you, so a burst of bounces on your first send is a bad start. Checking first removes dead addresses before they can bounce.
- Do I need to warm up a new sending domain?
- It's wise. Start with your most engaged contacts and increase the volume over several sends. Google's sender guidelines warn against sudden volume spikes from senders without a history of large sends.
- Can I keep my old SPF record when I add a new platform?
- Keep one SPF record and add the new platform to it, rather than creating a second SPF record. Once you've fully moved, remove the old platform from it.