The only thing worse than that is emailing them a simple boolean question and then your phone rings.
That’s a closure
When you aren’t feeling that async energy but you still get a callback.
I didn’t even register a callback. How the hell did code start randomly executing from here?
And then in the call you end up discussing what to put in the mail for “awareness”

Sounds like you should respond to that with a 400 Bad Request

The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).

Valid alternatives: 307 temp redirect to mailbox, 402 payment required to endure such pain or the classic 418. I’d go with the 418.
I might go with a 403 how dare you!
That’s a good one as well. 406, absolutely not acceptable, Sir!

Id ho with

415 Unsupported Media Type

or

426 Upgrade Required because it’s clearly the wrong protocol

x402 … charge for your time.