Public Preview: High Volume Email for Microsoft 365

scyto In you comment from 17-05-2024 08:55PM you stated that you got it working with the steps you took. Do you have Security Default enabled on you tenant. The documentation does state it will not work with that enabled, but then states some more bullets where I become confused as to whether it might still work when security defaults is enabled but you use the other bullet points?

I created the HVE account, did the powershell AuthenticationPolicy, went to Entra COnditional access and added an exclusing on the "Block all legacy sign-ins that don't support MFA" policy but still keep getting this error:

mail.Send error, send result: 535: 5.7.139 Authentication unsuccessful, basic auth is blocked. Contact your administrator.

So there is some place where Basic Auth is blocked....but where. Where could I reverse the "Security Default" feature If I wanted to... The docs do show where to enable, but now that only displays the "Manage COnditional Access" link.

I thought this might be a simple feature to allow an external call center to use this HVE account to send emails instead of the Mail Flow Connector because that is limited to de tenant restrictions