[sarchertech]

> Without API level idempotency, a single email on the client’s end could turn into many redundant emails at the service provider’s side, each of which could then be subject to those same subsequent duplications at the SMTP layer.

Ok so now there’s a 1/100 million chance that the client gets 3 duplicate emails.

I’m not arguing that idempotency is never important. The most popular blog post I’ve ever written is about the 2 generals problem and how idempotency can help.

I’m arguing in this specific instance it doesn’t matter.

As far as I was aware duplicate message-id headers aren’t deduped by every client, but if they are being used for deduplication just expose that in your api and let the caller set it.