Transactional emails rarely break in one loud place. They drift a little in the React form, a little in the API shape, and a little again in the background worker. Then somebody renames a field, the email still sends, and the customer gets a blank first name or the wrong CTA. It is a very normal bug, and it wastes more release energy than it should.
The pattern that helped my teams most is boring in a good way: treat email payloads as typed product events, not loose JSON blobs. The UI emits a contract, the API validates it, and the worker renders from the same schema. That removes a lot of "works on my machine" confusion before it reaches production.
Why typed email events matter in React apps
React teams move fast. Components get split, actions move into hooks, and feature flags change what data is available at submit time. Email code tends to lag behind that velocity because it lives one layer away from the shiny feature work.
What I keep seeing is this:
