Sure, but this is not a protocol, this is an API. APIs that allow actions that cost money, potentially annoy users / effect your reputation in the eyes of email recipients, I believe, should allow the caller to supply a unique key to enforce idempotency.

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esseph 6 hours ago | parent [-]

Track state on your side.

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johtso 4 hours ago | parent [-]

It’s impossible to know whether an action completed successfully if an error occurs between sending the request and persisting the result

	▲	esseph 3 hours ago \| parent [-]
		You also have no idea if it's been blocked or dropped before delivery unless you're using things like tracking pixels etc, right? And even then, that only works if they aren't being blocked (Proton Mail can do this, etc.) It just seems like this is trying to force something that was never remotely designed for it.