Mailer > Office 365 EOL Basic Auth, Moder Auth? #46732

If someone like me was trying to figure out how to solve this problem - most likely you should not:

1. There are no plans to disable Basic Auth for office365 SMTP:

We are not making any changes to SMTP Auth starting on October 1st. If it works today, it'll keep working from October 1st, until the day when SMTP Auth support for basic auth goes away (which has not been announced).

https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-september/bc-p/3619536/highlight/true#M34002

2. There are no scopes that allow you to send email using Modern Authentication in background Application.

Note As per the current test with SMTP Oauth 2.0 client credential flow with non-interactive sign in is not supported.
Moder Authentication

https://learn.microsoft.com/en-us/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth#smtp-protocol-exchange

Instructions on how to enable SMTP AUTH for new applications:
https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission#use-the-microsoft-365-admin-center-to-enable-or-disable-smtp-auth-on-specific-mailboxes

@zippytiff Perhaps this will be useful to you