Got a call from a client today that was in an Office 365 to Exchange 2010 on Premise Hybrid deployment. Users in Office 365 were unable to see Free/Busy information for on Premise users. I was able to get it resolved by doing the following steps.

  1. Logged into and tested the Free/Busy… Passed
  2. Logged into Exchange 2010 CAS server, opened EMS and ran “Test-FederationTrust -UserIdentity mailboxname -Verbose” . Everything also passed
  3. Checked the sharing policy on Exchange 2010 EMS and Exchange Online “Get-SharingPolicy | FL” . There was a small difference in the Exchange online so I added the Anonymous access by using the “Set-SharingPolicy” Command
  4. Checked the Permissions on the Virtual Directory on Exchange 2010 by running “Get-WebServicesVirtualDirectory | FL” . WSSecurity was enabled but I read that by refreshing the command some people were able to fix their issue, so I ran “Set-WebServicesVirtualDirectory -Identity “<HybridServer>\EWS (default web site)”-WSSecurityAuthentication $true”  Also did the same for AutoDiscover “Set-AutodiscoverVirtualDirectory -Identity “<HybridServer>\Autodiscover (Default Web Site)” -WSSecurityAuthentication $true”
  5. Then I refreshed the Metadata in Exchange 2010 EMS “Get-FederationTrust | Set-FederationTrust –RefreshMetadata”
  6. After that I reset IIS on all CAS and MBX servers and sometime after that everything started working properly again.