Office365 with oauth2 keeps sending smt_auth_disabled error

[JGitSchel]

Hi,

Im using MailKit and followed up the app coding in the oathexchange2 example.
But after authentication and trying to send the message, it throws the error authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant.
But I'm using the oauth2 with this MailKit code.. why this error?

[jstedfast]

SMTP, POP3 and IMAP are all disabled by default in Office365 Exchange Tenants. You need to enable them.

[JGitSchel]

Thanks a lot for your reply.
I'm sorry, but yes I know.
I've asked IT and they told me that smtp_auth is disabled and later on this year isn't supported anymore by microsoft and that I have to use oauth2.
Thats why I'm using MailKit.. but again.. after creating an oauth token it receives isAuthenticated=true in its result.. but with an error Credentialswrong and message about smtp_auth.

This subject is new to me, I'm reading a lot about it to implement it to our software for supporting office365 to our customers, but as far as I read, oauth2 will still be supported by office365.
I've tried a lot of options, but all ends up in the error about smtp_auth.

I've added smtp.send in the azure app, also including mail.send, receive, writeread etc.
I've tried multiple combinations. But none works.

So my (N00b) question about this subject is..
Is this based on the same smtp_auth which will be removed from office365, or can I still keep using this library after that?
Next one, i've logged some steps and see an succesfully token and connection to smtp.office365.com, using bearer etc.
Next a nice Hello from our office365 server (internal server).
Then the authenticationasync starts and it fails.
Could you give me a simple hint where to start?
Im already couple of days busy with logging, tracking, changing, including IT.. but haven't any clue what's going wrong.

[jstedfast]

Is this based on the same smtp_auth which will be removed from office365, or can I still keep using this library after that?

What Microsoft means is that they will stop supporting password-based authentication. OAuth2 uses token-based authentication. So yes, you'll be able to use MailKit with OAuth2 once Microsoft stops supporting password-based authentication.

Could you give me a simple hint where to start?

I always recommend starting with the documentation - make sure you read it thoroughly and follow every step correctly. If you do that, it will work for you. If you don't, you'll get errors and those errors won't be helpful in tracking down the problem in my experience.