How do I move my email list to a new platform without hurting deliverability?

The safest approach is to treat the move as a change in sending infrastructure, not a reason to send your whole list at once. Keep your sender identity and audience expectations steady, then ramp up based on how recipients and mailbox providers respond.

Before the move

1. Export the full contact history, not just email addresses: consent/source and signup date, tags, segments, engagement, bounces, unsubscribes, and complaints.
2. Carry over suppression records. Do not re-import unsubscribed, bounced, or complained-about addresses as mailable contacts.
3. Clean the list. Remove invalid addresses and avoid sending to old or unengaged contacts just because they’re in the export. Use only people who gave permission to receive your messages.
4. Authenticate your domain in the new platform before sending. Configure SPF and DKIM, and check DMARC alignment. Gmail requires SPF, DKIM, and DMARC for bulk senders; Yahoo has similar bulk-sender requirements. (support.google.com)
5. Test the basics: From address and reply-to, unsubscribe link and one-click unsubscribe, templates, links, forms, and any automations. Keep the From name and content recognizable to subscribers.

During the move

1. Start with your most engaged subscribers—for example, people who clicked or otherwise interacted recently—then gradually expand to less-recently active groups. Don’t send a sudden full-list blast from the new setup. Google specifically recommends increasing volume gradually and monitoring delivery, spam rates, and reputation. (support.google.com)
2. Keep the sending pattern familiar. Maintain a similar cadence and message type where possible; avoid combining the platform move with a new sending domain, major branding change, and large volume increase.
3. Monitor each send for bounces, deferrals, complaints, unsubscribes, and inbox placement. If those worsen, pause the ramp-up, investigate, and reduce volume rather than pushing ahead. Google advises slowing down when bounces or deferrals rise. (support.google.com)

After launch

1. Keep both platforms coordinated briefly so new signups and unsubscribes aren’t lost during the transition. Then turn off the old platform’s campaigns and automations to avoid duplicate sends.
2. Watch the first several campaigns closely. The right ramp-up speed depends on your usual volume, how recently people engaged, and whether you’re also changing domains or IPs—there isn’t one universal schedule.

One useful rule: don’t “warm up” by emailing inactive people to see who responds. Start with your strongest, permission-based audience and expand only while the signals remain healthy. For Gmail, keep reported spam rates below 0.3%; Yahoo also specifies a rate below 0.3%. (support.google.com)

Moving a list without losing deliverability comes down to three things: send less but better-quality mail, authenticate the new sender before it sends, and ramp volume gradually. Here's the sequence.

1. Clean the list before you export anything
Validate every address and look for hard bounces, dead domains, and spam traps. Catch-all and "risky" results deserve extra attention. On your existing ESP they benefited from your established reputation, but on a new platform with no sending history they're more likely to bounce or trigger spam filters. Remove invalid, duplicate, and long-inactive addresses too.

2. Segment by engagement
Opened or clicked in the last 90 days is a common cutoff for your core group. Some guides use a tighter 30-day window for the first wave. Contacts who haven't engaged in over 180 days shouldn't be migrated until your new platform's reputation is established. Some of them should be suppressed permanently.

3. Bring over suppression data first
Export unsubscribes, hard bounces, and spam complaints from the old platform and import them into the new one before any sending. This is the most commonly skipped step, and the most dangerous to skip. Verify the import by spot-checking a few known suppressed addresses.

4. Set up authentication before sending
Add the new platform's SPF include and DKIM alongside the old ones rather than replacing them. Add the new ESP's SPF include before it sends any email, configure its DKIM alongside the old one, and don't remove the old ESP's records until migration is complete. Also confirm DMARC is published and aligned. Watch your SPF lookup count, since adding a second sender can push you over the limit.

5. Warm up gradually, using a dual-send
Warm-up matters most if you're getting a dedicated IP. On a shared IP, your ESP manages the pool's reputation, so you don't need to warm it yourself. A dedicated IP, or one dormant for 30+ days, needs a structured ramp. Expect the full process to take about 4-6 weeks. A common approach is to keep the old platform running for the full list while shifting segments to the new one in stages, such as 10%, 30%, 60%, 90%, then 100%. That way you can roll back if something breaks. A flip-the-switch migration can drop inbox placement sharply for several weeks.

6. Watch the right metrics

• Spam complaints: Google recommends staying below 0.1% and never reaching 0.3%. Google recommends keeping Postmaster Tools spam rates below 0.1% and avoiding 0.3% or higher.
• Bounces: One guide suggests pausing if bounces climb above ~2% in week one and fixing your data before scaling.
• Engagement: Compare opens and clicks between the old and new platforms. A significant gap usually signals a delivery problem.
• Authentication: Check DMARC reports to confirm both platforms pass.

Expect some initial dip. One source notes an adjustment period that typically lasts 2–4 weeks with consistent, gradual sending, so judge trends over time rather than single sends.

7. Keep everything else stable
Avoid big design or subject-line changes right after the move. Recreate your automations and transactional emails on the new platform and test each one before going live. Make sure one-click unsubscribe works, since Gmail and Yahoo require it for bulk senders.

Bulk sender rules: If you send 5,000+ messages a day to Gmail or Yahoo addresses, you must have SPF, DKIM, DMARC with alignment, and one-click unsubscribe. The sources I found vary on exact spam-rate thresholds, so check the current Google and Yahoo sender guidance before you finalize your setup.

Moving your email list to a new platform is a critical transition that requires a strategic, phased approach to protect your sender reputation. Because mailbox providers (like Gmail and Outlook) do not automatically trust new infrastructure, treating the move as a technical "import" without a deliverability plan is a common cause of inbox placement drops.

Follow these steps to migrate without damaging your deliverability.

1. Clean Your List Before You Move

Never migrate "dead weight." If you move inactive or invalid addresses, your first send will trigger a spike in hard bounces and spam complaints, which tells mailbox providers your new account is suspicious.

• Audit and Prune: Remove all hard-bounced, unsubscribed, and chronically inactive contacts from your current platform before exporting your list.
• Use Verification Tools: Before importing to your new platform, run your list through a professional email verification service. This catches invalid syntax, disposable emails, and potential spam traps.
• Bring Suppression Data: Ensure you export your "suppression list" (the list of people who previously opted out) from your old provider and import it into the new one to avoid emailing people who have already unsubscribed.

2. Prepare Technical Authentication

Before sending any marketing emails, you must establish trust at the DNS level.

• Configure Records: Set up SPF, DKIM, and DMARC for your sending domain on the new platform. These act as your "digital passport," proving to providers that your new platform has permission to send on your behalf.
• Verify Sender Details: Ensure your sender address and domain are fully authenticated.

3. Implement an IP/Domain Warm-up Strategy

Even if you are using a shared IP, you must "warm up" your sending domain. Mailbox providers treat new sending activity with caution; a sudden blast to your full list will trigger filters.

• Start with Your Best: In your first few sends, target only your most engaged subscribers (those who have opened or clicked in the last 30–60 days). Their high engagement levels signal to providers that you are a legitimate, welcome sender.
• Gradual Scaling: Increase your volume incrementally over 4–8 weeks. A common approach is to double your volume every few days, monitoring for bounces and complaints at each step.
• Monitor Closely: Watch your metrics daily during the migration. If you see a spike in bounce rates (>2%) or spam complaints (>0.1%), pause your sends and investigate immediately.

4. Maintain Continuity

• Don't Rush: If possible, keep your old platform active for a short period (parallel sending) to handle any final legacy automations or until you are confident the new setup is performing as expected.
• Update Integrations: Ensure your CRM, signup forms, and automated flows (like welcome emails) are fully tested and connected to the new platform before you switch.
• Set Expectations: If you are changing your "From" name or branding, send a notification email to your list beforehand so they recognize the sender and are less likely to mark you as spam.

Summary Checklist

To protect deliverability, treat the move as a gradual transition—not a one-time bulk send.

1. Set up the new sender before importing or sending. Authenticate your sending domain with SPF and DKIM, and publish DMARC. Make sure the domain in your visible “From” address aligns with the authenticated domain. Gmail requires SPF, DKIM, and DMARC for bulk senders, and Microsoft has similar requirements for high-volume senders. ¹⁴

1. Move consent and suppression data. Import only people who opted in, along with their consent/source and engagement details. Bring over unsubscribes, complaints, hard bounces, and other suppressed addresses, and make sure the new platform won’t email them. Never use the move as a reason to re-contact people who opted out. ¹²

1. Clean the list before the first send. Remove invalid or repeatedly bouncing addresses, and be cautious with old or unengaged contacts. Start with recent, active subscribers; they’re more likely to engage and less likely to generate complaints. ¹⁰¹²

1. Warm up gradually. Begin with your most engaged subscribers, keep a steady cadence, and increase volume in stages as results stay healthy. Don’t send your entire list on day one. The right pace depends on your normal volume, the new platform’s sending setup, and how your audience responds. ¹⁰¹²

1. Keep the message and unsubscribe experience familiar. Use the same recognizable From name and domain, and include a clear unsubscribe link. For marketing mail to Gmail, one-click unsubscribe is required; make sure opt-outs are processed promptly. ²

1. Monitor closely and pause increases if signals worsen. Watch delivery failures, hard bounces, spam complaints, unsubscribes, and engagement by recipient provider. If complaints or bounces jump, stop scaling, investigate the affected segment or setup, and resume only when corrected.

1. Plan the cutover carefully. If you send at high volume, you may be able to shift portions of the campaign from the old platform to the new one rather than switching everything at once. Avoid sending the same campaign to the same people from both systems, and keep the old platform available until you’ve verified authentication, suppression syncing, and unsubscribe handling.

Before launch: send test messages, verify SPF/DKIM/DMARC results in the headers, test unsubscribe end to end, and confirm your suppression list is applied. If you share your approximate list size, current sending frequency, and whether the new platform uses a dedicated or shared IP, I can suggest a more tailored migration sequence.