Following an issue with Free/Busy in Exchange online, earlier this week, I was troubleshooting the exchange of Free/Busy information in some of my hybrid deployments as Free/Busy information was still not working.
After having checked some (obvious things) like the Organization Relationships and whether or not Autodiscover was working properly, I discovered an issue when running the Test-FederationTrust cmdlet.

In fact, the cmdlet completed almost entirely successful, except for the very last step in the process:

Id         : TokenValidation
Type       : Error
Message    : Failed to validate delegation token.

This also explained why I was seeing 401 Unauthorized messages when running the Test-OrganizationRelationship command.

I then checked the same in some of my other deployments and found out the all had the same issue. At least, there was some common ground to start working from.
I turned to co-MVP Steve Goodman and asked him to run the same command in one of his labs in order to have a point of reference. At the same time, he asked me to run a command which might help:

Get-FederationTrust | Set-Federationtrust –RefreshMetaData

After running the command, I re-ran the Test-FederationTrust command which now completed successfully.


Although the Free/Busy issues in Office 365 should be solved, some customers might still experience problems exchanging Free/Busy information. In this case, the problem manifests itself by e.g. online users not being able to request on-premises user’s availability information.


  1. Was issue with Free/Busy in Exchange Online last week a problem at Microsoft? We experienced the same issue, and it it still not working.

    1. Hi,

      yes there were some Free/Busy issues, but not everyone was impacted. So it’s very difficult to point this exclusively to that issue. What exactly is your problem right now? Free/Busy in an hybrid organization not working?


      1. Yes, I get “Can’t get event for one or more calendars” in OWA when trying to view an on-premise calendar from Exchange Online. Test-FederationTrust returns no errors, and autodiscover is working. This started sometime last week.

  2. in our scenario, free busy only to 2007 mailboxes stopped working. test connectivity is yelling saying that my version of the availability service is incorrect and needs to be 2010 or higher. it worked fine up until this. is that the same scenario you saw?

    1. Jim,

      sorry for the late reply (somehow comments always seem to escape my attention 😦 )
      actually how Exchange 2007 handles availability information is completely different from Exchange 2010 or 2013 as the former has no way of interacting with the MFG. Exchange 2007 doesn’t have the native Exchange Federation features like 2010 or 2013.

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