What are risks during ESP migrations?
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You're switching to a new ESP and your stomach's tight. Those worries are justified. Migrations aren't just a matter of flipping a switch. They introduce real risks that can tank your delivery and damage your sender reputation if you're not careful.
The reputation gap. New IP addresses need warming. If you send at full volume on day one, you'll look like a spammer to inbox providers. You're arriving with zero history and zero positive signals. Meanwhile, your domain reputation might shift too if your sending patterns change dramatically. That gap between old signals and new ones getting built is where problems hide.
Authentication breaks. During the transition, SPF and DKIM records get messy. DNS updates don't happen instantly. If you miss updating your records or they're not in sync with your new ESP, authentication failures spike and DMARC alignment breaks temporarily. Blocklist problems follow.
Suppression data disasters. Bounced addresses don't transfer automatically. If you don't import them into your new ESP, you'll email them again and damage your reputation. Unsubscribes go missing. Suddenly you're mailing people who opted out, creating a compliance nightmare. Complaint data doesn't move either, so repeat offenders complain again.
Data loss and broken automations. Historical engagement data can vanish or fail to migrate. Subscriber segments and preferences get lost in translation. Tracking links in old emails break. Automations don't replicate correctly. Your CRM integrations aren't updated. Webhooks point to dead endpoints.
Timeline pressure. Contract deadlines push you to rush. You don't allow time for proper IP warming. Testing gets skipped. You go live unprepared.
Next step. Build a migration checklist with phase gates. Plan for at least 30 days of gradual warmup, starting at 10% of your normal send volume and increasing weekly. Verify suppression lists are imported before the first send. Test authentication setup, automations, and integrations in a staging environment first. Document everything.
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