Microsoft, SMTP, and OAuth2.0 [Workaround proposed]

Less of a C# question and more of a Microsoft question:
MS has advised that they're deprecating SMTP basic auth starting October 1st.
(https://docs.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basic-authentication-exchange-online)

We have services sending automated emails using SMTP. There's no SMTP permission for the Office365 Exchange API and Graph doesn't have it available as an application permission (it's delegated only, meaning a user must be present, which defeats the purpose of automation)

So how are we supposed to send automated emails under the OAuth 2.0 paradigm?

SendGrid

Yeah, or Gmail. Plus we'll be spared the first wave of deprecation at least, so thankfully this isn't urgent.

I'll gleefully tell my boss we're wasting our money on the O365 subscription...

I'm not sure if O365 is supposed to be used for automated email

The smtp endpoint might just be to connect clients like firebird

or whatever the mozilla thing is

thunderbird

There are a number of reasons to use tech like sendgrid, mailgun, etc, one of them is that sending email reliably is hard. Email services have low bounce rates, follow proper standards, etc. That way you can be a good email citizen.