Forum Discussion
401 Unauthorized when accessing /messages api using client credentials grant flow
I have a mailbox in on prem exchange server (which is in hybrid mode) abc@onprem.com and i am trying to access this via graph api (/messages). This works perfectly if i do this in graph explorer, but...
Karthik_Hebbar We are struggling with exactly the same. What I thought we could do was to use delegation (and using resource owner grant).
I am going to take a look into the Exchange's binaries to see if I can figure what needs to be done. What I found so far, is that when you look at Get-PartnerApplications, there is Graph registered, but it doesn't have any AppOnlyPermissions set which could be the issue (but as per docs it is internal field only for MS...).