The hidden cost of building your own email integration

Most teams that build a custom email integration do a reasonable job scoping the initial work. They estimate the OAuth flow, the API calls, the data model, and hand it to engineering. The first version ships. The demo works. What they don’t scope is everything that comes after. Post-launch, the maintenance burden on a custom email integration accumulates across providers, edge cases, and infrastructure the initial build never touched. This post breaks down where those costs actually live and why they’re so easy to miss before the first line of code is written.