I have a comment and a question.
If the Oauth aspect is the biggest challenge, look for @samliew’s responses to that…
One of them is here:
My question: what is not working from the reddit post? In-Reply-To means that there was an email to reply to. I’m trying to understand why you would want to have that in the first email of the thread. Normally, that only appears in the second email in a thread, i.e. a response.
L