I am getting Unauthorised error without reason while subscribing to email notification using graph API

Hello @Yamin Lawar ,

I understand that you have an application registered in Entra ID with all the required permissions configured to fetch emails and receive notifications. You've implemented the client credentials flow and successfully tested it using your personal Azure accounts — you were able to fetch emails and receive notifications when new emails arrived in the subscribed inbox.

However, after migrating to your enterprise Azure account, the same code is now failing with authorization errors.

There is a maximum limit of 1000 active subscriptions for Outlook resources per mailbox for all applications. You can subscribe to changes in contacts, events, or messages in the mailbox.

Depending on the resource, use the least privileged permission specified in the following table to call this API

Note the following limitations:

1. Delegated permission supports subscribing to items in folders in only the signed-in user's mailbox. For example, you can't use the delegated permission, Calendars.Read to subscribe to events in another user’s mailbox.
2. To subscribe to change notifications of Outlook contacts, events, or messages in shared or delegated folders:

• Use the corresponding application permission to subscribe to changes of items in a folder or mailbox of any user in the tenant.
• Don't use the Outlook sharing permissions (Contacts.Read.Shared, Calendars.Read.Shared, Mail.Read.Shared, and their read/write counterparts), as they do not support subscribing to change notifications on items in shared or delegated folders.

Make sure to extend a subscription before it expires. The maximum lifetime for a subscription without Outlook resource data can be found in the subscription lifetime table.

If you lose the permission granted earlier for a subscription and the subscription expires meanwhile, request permission again to create a new subscription.

Subscriptions have a limited lifetime. Apps need to renew their subscriptions before the expiration time; Otherwise, they need to create a new subscription. Apps can also unsubscribe at any time to stop getting change notifications.
The following table shows the maximum expiration times for subscriptions per resource in Microsoft Graph.

Note: Existing applications and new applications should not exceed the supported value. In the future, any requests to create or renew a subscription beyond the maximum value will fail.

For detailed information follow the documents: https://learn.microsoft.com/en-us/graph/outlook-change-notifications-overview#create-a-subscription , https://learn.microsoft.com/en-us/graph/change-notifications-overview#subscription-lifetime

Hope the above Information helps. If you are still facing the issues. Provide me the screen shot error that you are getting.

Hello @Yamin Lawar ,

Following up to see if the above information in helpful. Let us know if you have any additional queries. Happy to assist you further.

Hello @Goutam Pratti

On the detail answers you suggested, here is more information

1. There is a maximum limit of 1000 active subscriptions for Outlook resources per mailbox for all applications. You can subscribe to changes in contacts, events, or messages in the mailbox.

There is no subscription yet made on current application so this points is checked and doesn't apply here.

2. Regarding limitation:

I have already checked all the limitations and I am using application permission already not a delegate permission and just for information I am subscribing to email (i.e messages only)

3. Extending subscription:

I already have to renew subscription 24 hours before it expire but please understand even we are not able to create subscription so there is no point of looking at this.

Sorry but your above information is very general and we follow all the instruction listed in documents please can you help us to guide what exactly going wrong here, if we can get any developer or technical person support?

Hello @Yamin Lawar ,

As you mentioned that you're encountering an "Unauthorized" error, could you please share a screenshot of the error? This will help us troubleshoot the issue more effectively.

Here I am attaching screenshot for your reference

For more context this user is part of our organisation and I can able to fetch users list and this user is available in response of users list which I fetched through same code base and credential using Microsoft Graph API