Office 365 to Exchange 2010 on prem calendar free/busy information

Posted by robd on August 22, 2018
exchange 2010

Hello,

Preface this post by saying a man from Exchange support said “This is the most complicated Exchange environment I’ve ever seen”.

That said this issue is pretty common and hopefully this post will help someone else.

We have an Exchange 2010 to 365 hybrid environment that look a bit like this:

We had an issue where users on our 365 tenancy couldn’t see on the Exchange 2010 on-premises free/busy info for users in Group2.contoso.com.

Now I know what your thinking, just compare the settings on Group1 to Group2, well due to company rules and politics I can’t….I can only troubleshoot group2 and the servers there.

So first things first, check users permissions and setup a test user and find the error in Outlook:

Thanks to Babunski and his post I found this really good troubleshooting guide and everything looked ok:

https://support.microsoft.com/en-us/help/10092/troubleshooting-free-busy-issues-in-exchange-hybrid-environment

  • Firewall is fine,
  • Network is ok,
  • DNS surprising is working,
  • Check Exchange online tool:

https://www.testexchangeconnectivity.com

  • 365 to prem relationship is ok:

  • IIS Logs look ok, %SystemDrive%\inetpub\logs\LogFiles

  • EWS logs look ok, %SystemDrive%\inetpub\logs\LogFiles

  • Checked the external URL – seems ok.

  • Check the IIS permissions with – this looked ok

  • Checked IIS EWS and Autodiscover:

  • Checked more relationship stuff – all ok

Next – contact support!  🙁

 

Before I contact support I did find one more URL that suggests to check the certs and import the cert you used to setup the federation onto the CAS server which unfortunately didn’t work for us:

https://support.microsoft.com/en-gb/help/3057905/exchange-online-users-cannot-access-free-busy-information-of-users-in

 

Soooo here I am, time to contact support.

 

The first thing they checked was the local url on the client access server:

https://ClientAccessGroup2Server1.group.contoso.com/ews/exchange.asmx

So there’s an issue, basically we didn’t add the server to our wild card cert.  So added the server names as Subject alternative names and imported it using PowerShell onto both Client access servers and then rebooted:

Fixed:

Checked the URLS set in Exchange:

Our internal URL was actually set to Client Access array for Contoso rather than group2.contoso.com so we changed this:

And rebooted again.

 

Next we disabled and re-enabled ISS security (this broke OOF for a while, we had to run this twice):

So here are stuck…..

 

MS ran some traces using Extra:

 

And went away for a while and came back with:

Internet facing Site Conotso.com is able to look up the user and send a request to Group2 servers.

The request failed with an empty response.

On group2 server we notice below error,

 

So the long and short of it is they think IIS is broken. The traffic is being passed to the Group2 services but these services are not passing the information back up the stream.

 

MS decided they wanted swap out the EWS web.config with a new one from:

 

The reason being in the config file it was referencing:

And it should be referencing (or where ever you install of Exchange is):

And another reboot.

 

Next we checked the logging from Outlook:

Which dumps files too: %Temp%\outlook logging

And they found this error:

 

This prompted MS to check the IIS bindings which were wrong

So we added some missing bindings using these command:

No change and still the same error: Response Code ErrorProxyRequestProcessingFailed

 

So we checked windows services and would you believe it but these dot net services were not installed:

net.tcp lisener adapter

net.pipe listener adapter

 

So we installed the missing features:

Rebooted both.

And Boom we are working!!!!!!!!!!!!!!!!!!!!!

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