Day CQ Mail Service and OAuth

Hi, our AEM instance uses the Day CQ Mail Service for workflow notifications and connects to a MS Office SMTP server using basic authentication (username/password). I have a requirement that needs to change this from basic authentication to something more modern like OAuth.

I found this documentation and seems pretty straightforward but we are missing the "OAuth flow" checkbox in the Day CQ Mail service settings and I do not see a configuration for "CQ Mailer SMTP OAuth2 Provider." We are running 6.5.8 if that helps.

Thanks in advance!