Create folder in user mailbox with Graph API - azure-ad-graph-api

Question

want to use the Graph API to create a folder in a user's mailbox that exists in Exchange Online.
As a result of the investigation, if I use "https://graph.microsoft.com/v1.0/users/testuser01#domain.com/mailFolders", I feel that it is possible, but an error is displayed and I cannot create it.
Currently, "Exchange> Mail.ReadWrite, MailboxSettings.ReadWrite" is assigned to the execution user (admin).
However, it says "Access is denied. Check credentials and try again." Is the permission wrong?
Or is the specified URL incorrect?
Sorry to trouble you, but thank you for your response.
【Append】
$body = #{
grant_type="client_credentials"
resource=$resource
client_id=$ClientID
client_secret=$ClientSecret
}
`#Get Token
$oauth = Invoke-RestMethod -Method Post -Uri $loginURL/$TenantName/oauth2/token -Body $body
API Permissions

Answer 1

You are using the client credential flow to get the token to call Microsoft Graph - Create MailFolder, so you need to add the Application permission Mail.ReadWrite of Micrsoft Graph to your AD App.
1.Add the Application permission Mail.ReadWrite like below.
2.Click the Grant admin consent for xxx button, and make sure the $resource in your request is https://graph.microsoft.com.
Update:
Here is a powershell sample to call Create MailFolder API to create MailFolder.
$uri = "https://graph.microsoft.com/v1.0/users/joyw#xxxxx.onmicrosoft.com/mailFolders"
$headers = #{
'Content-Type' = 'application/json'
'Authorization' = 'Bearer <access-token-here>'
}
$body = ConvertTo-Json #{
"displayName" = "testfolder1"
}
Invoke-RestMethod -Method Post -Uri $uri -Headers $headers -Body $body
Check the result in the Graph Explorer with List mailFolders: