While using using Sign up invitation flow in Azure B2C using custom policy, I want to send invitation email to user using Microsoft native email provider. I want to use the Microsoft native email provider which is generally used by MS while sending verification code or OTP for example during Forgot password flow journey.

I am aware of the solution of using 3rd party mail provider like SendGrid , Mailjet or SendInBlue. Hence please ignore them.

I have tried the 3rd party email provider like SendGrid and that works well. But i am not seeing any documentation with regards to sending email using msonlineservices.