Why do ESP migrations go sideways?
ESP migrations go sideways when teams move assets before they understand behavior. Templates are visible, but triggers, suppression rules, list hygiene, and reporting assumptions carry the real risk.
The migration should begin with an inventory of what fires today, why it fires, and whether it still deserves to exist.
What should be migrated first?
Low-risk sends should move first. That gives the team a chance to validate deliverability, reporting, and QA patterns before revenue-critical flows move.
High-volume lifecycle programs should have test users, rollback notes, and launch watch.
What makes a migration successful?
A successful migration leaves the team with cleaner logic than it started with. The destination ESP should have fewer mystery segments, clearer naming, and documentation operators can use.
The win is not just being on the new platform. The win is being able to ship confidently after the cutover.