Signup email delivery looks simple until retries start stacking up. A client times out, the user taps submit again, and now the same account may get two confirmation emails with different lifetimes or different audit trails. In a REST API, that is not just annoying. It makes Authentication behavior harder to explain, harder to test, and harder to support once prod traffic gets noisy.
Teams searching for get temporary email flows or tp mail so are often trying to isolate inboxes for testing, but the deeper backend issue is idempotency. You want one logical signup attempt to produce one durable email intent, even if the transport layer or the worker retried more than once.
Why signup emails become duplicated
Most duplicate signup emails are caused by two things happening at the same time:
the API does not persist a stable request identity before enqueueing work
