What is your system for keeping welcome email sequences up to date?

I recently went through our user onboarding sequence pretending to be a fresh signup.

It was eye opening to see how many messages were repeating steps or explaining features that don't even exist in the app anymore.

New users are the least patient when things don't make sense so confusing emails can easily drive them away. Fixing it didn't take long but keeping these flows accurate requires a real process.

How do you make sure your welcome messages get updated whenever the product changes?