I am converting .NET application which currently reads Google Mail to Office365 Outlook as my employer moved email solution.
I am using the Microsoft Graph API. It is configured as an Azure Active Directory App registration. It uses "Application permissions" to access a shared mailbox.
Initially the application worked fine as I can access the messages in the inbox mail folder. However after few hours I get Access to OData is disabled error message.
So far I have registered 3 apps and granted mailbox access by following this link. https://learn.microsoft.com/en-us/graph/auth-limit-mailbox-access
They all work for few hours and after that it gives 403 error.
(1) Still can you repro the issue. If yes, share the detailed response (along with timestamp, requestid) (2) When you notice the above error, when you try to access your mailbox or shared mailbox? (3) Finally, i would suggest you to try the same with POSTMAN and see if you can repro the issue or not. (4) Sound like an Access policy to me, so configure the ApplicationAccessPolicy correctly, test it thoroughly in PROD and handle the API errors in your application.