Hi @Craig Zivolich,
Based on your query, we understood that you would like to add the API permissions for app registrations to authenticate legacy protocols.
Here is the Microsoft document which helps you in configuring the application: Authenticate an IMAP, POP or SMTP connection using OAuth. Please make sure you have the licenses you have for your organization. Also, please make sure you trying to add permissions with either global admin or application developer roles.
We have provided you the configuration you need to perform from Entra App registration. I hope this information is helpful. Please feel free to reach out if you have any further questions.
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