I want to be able to get the number of unread emails for an specific name in my tenant.
Something like: https://graph.microsoft.com/v1.0/me/mailFolders/Inbox/messages?$filter=isRead ne false&$count=true]
but be able to change the me for an specific user, the above works in graph explorer for my signing user.
I tried this example here. Which bring me a list of users and was trying to modified it without success.
the app have api permission for microsoft graph to read mail in all mailboxes.
To access a users mailbox other than the signed in user. You will need to call the api with an application (app-only) token. This will require requesting application permissions (not delegate permissions) for Mail.Read.
More information on getting access without a user context is available here https://docs.microsoft.com/en-us/graph/auth-v2-service?context=graph%2Fapi%2F1.0&view=graph-rest-1.0
The request would be GET https://graph.microsoft.com/v1.0/users/{id | userPrincipalName}/messages
You can use the id from calling GET https://graph.microsoft.com/v1.0/users
or use the upn which is their email address in most cases that you may already have.
More documentation is available here https://docs.microsoft.com/en-us/graph/api/user-list-messages?view=graph-rest-1.0&tabs=http
You can actually test these request calls in our Postman collections. Graph Explorer is purely for on-behalf of flow request calls. Setup instructions are here https://docs.microsoft.com/en-us/graph/use-postman
I may be misunderstanding your question, but I think your trouble is you're replacing me in the URI with the user identifier. If that's correct, you need to replace it with user/useridentifier instead.
That would make the query:
https://graph.microsoft.com/v1.0/user//mailFolders/Inbox/messages?$filter=isRead ne false&$count=true
