Exchange 2016 Migration to a new Organization - Free/Busy

[Robert Styles]

Working on a company migration of users into a new Exchange Org. We have a migration process but would like to use Free/Busy during the migration period. Has anyone been able to get free/busy working? I've not found any clear guidance and some of what I've found mentions some sort of directory sync is needed. Is this a supported option? If anyone has steps on how to get the free busy working, a checklist or something I would greatly appreciate the knowledge share.

[#2]

You are not very clear on the details, but generally speaking you need to establish an org relationship between the two orgs: https://docs.microsoft.com/en-us/exchange/sharing/organization-relationships/organization-relationsh...

[#3]

The existing organization (OrgA) can not retrieve the sts token when you run the test-organizationrelationship, we get STEP 3 - Requesting, then step 4 returns with FailureToGetDelegationToken.

On the other organization (OrgB), the user name we are trying to reach in OrgA is not even recognized when the test-organizationrelationship is run. 

This organization is big on security and has most of exchange excluded from public access so I'm wondering if it's even properly connected with the Microsoft federation gateway.