Email Migration Checklist

Switching email platforms is one of the highest-risk operations in marketing. Get it wrong and you lose subscribers, break automations that drive revenue, tank your deliverability, and potentially violate CAN-SPAM or GDPR by losing suppression lists. Get it right and the whole thing is invisible to your subscribers. This 32-item checklist covers every phase of migration so nothing slips through the cracks.

Phase 1: The Pre-Migration Audit (Don't Skip This)

Before you touch the new platform, document everything on your current one. Export your complete subscriber list with all custom fields, tags, segments, and engagement history. Export your suppression list separately—this includes every unsubscribed, bounced, and complained address. Forgetting to migrate suppressions is the #1 migration disaster because you'll email people who explicitly opted out, generating spam complaints that can blocklist your domain within days. Also document every automation flow, noting triggers, delays, conditions, and content.

Phase 2: Authentication and Infrastructure

Set up SPF, DKIM, and DMARC for the new platform before sending a single email. If you're moving to a new IP, you'll need to warm it up—start with 50-100 emails/day to your most engaged subscribers and double every 2-3 days over 4-8 weeks. Use the warmup calculator to plan the schedule. Verify all DNS records are propagated with the DNS propagation checker before proceeding. This phase takes 1-2 weeks on its own.

Phase 3: The Scariest Part—Data Migration and Parallel Running

Import your subscribers to the new platform and verify counts match exactly. Check that custom fields mapped correctly—a common failure is date formats (MM/DD vs DD/MM) getting mangled during import. Import your suppression list and verify it's enforced. Rebuild your automations in the new platform but keep them paused. Run both platforms in parallel for 1-2 weeks: continue sending from the old platform while testing everything on the new one. This overlap period is your safety net.

Phase 4: Go-Live and the Danger Zone

When you flip the switch, disable all automations on the old platform first, then enable them on the new one. Send your first real campaign to a small, engaged segment (top 10% by engagement) and monitor bounce rates, complaint rates, and deliverability for 24-48 hours. If everything looks clean, gradually increase to full volume. Watch your bounce rate obsessively for the first two weeks. Check the blacklist checker daily during this period. Keep your old platform account active for at least 90 days in case you need to reference historical data or roll back.

Common Migration Disasters and How to Avoid Them

The three most common disasters are: 1) Lost suppression lists—emailing people who unsubscribed, generating a wave of spam complaints. 2) IP warmup failures—sending full volume from a cold IP and getting blocked by Gmail. 3) Broken automations—triggers firing incorrectly and sending duplicate or irrelevant emails to your entire list. Each of these is completely preventable with proper planning. The checklist below walks you through the specific steps to avoid each one.