Hi @Sam
However, to do that, Basic Authentication needs to be on for the tenant, which as far as I can tell, is now impossible to do.
Yes. To use basic auth for SMTP, you may need to disable security defaults for the tenant.
If it is not possible, you may need to update the application to use modern auth.
Please refer to this link: Basic Authentication Deprecation in Exchange Online – May 2022 Update
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