Trying to hit a basic Target API call through postman, following the instructions found here: https://developers.adobetarget.com/api/delivery-api/#section/User-Permissions-(Premium)
Getting the following error: HV000028: Unexpected exception during isValid call
I have provided the property token and local mbox name in the POST API, I was able to get the 200 response
POST > https://xxx.tt.omtrdc.net/rest/v1/delivery?client=xxx&sessionId=100290adcb6a14043309f8789b21b0c18ba
Body as raw > json
Can you try with some local mbox nae and not the global mbox name ?