Exchange 2007 and Exchange Online Free/Busy Issue

I can't sing higher praises on the Exchange Hybrid Free/Busy Troubleshooter - available here https://support.microsoft.com/en-au/help/10092/troubleshooting-free-busy-issues-in-exchange-hybrid-environment

It got me out of a jam that was especially perplexing.

So I have an Exchange 2007 environment, and the customer would want to move all mailboxes to Exchange Online, but they want to deploy Exchange Hybrid because "Big Bang" doesn't work for them.

So I put in an Exchange 2013 "hybrid" server and ran HCW. All went fine except when an Ex07 user tries to query free/busy for a cloud/EXO user, the dreaded grey bar "No Information" is shown.

FIX: Exchange 2013's EWS InternalURL is set to the wrong URL - in my case, it was pointing to the UAG 2010's listener, which still publishes OWA 2007. So I did the following to fix it:

• Update Exchange 2013 EWS InternalURL to internal FQDN (so the Exchange 2007 can locate it) - EAC > Servers > Exchange 2013 Server > EWS (Default Web Site) > Internal URL Then perform IIS reset
• Removed the availability space object - Remove-AvailabilityAddressSpace -Identity ‘tenantname.mail.onmicrosoft.com' 
• Recreate the availability space object - Add-AvailabilityAddressSpace -ForestName tenantname.mail.onmicrosoft.com' -AccessMethod 'InternalProxy' -UseServiceAccount $true -ProxyUrl https://exchange2013internalFQDN.company.com/ews/exchange.asmx

HCW v3 Stuck at "Adding Federated Domain"

Exchange Hybrid Configuration Wizard - always interesting times every single time I run this wizard.

My customer has three public facing domains that is required as part of the Exchange Online migration. I've added them into Verified Domain in Office 365 portal, ran HCW v3, added the TXT records required for Microsoft Federation Gateway, and when I clicked on "Verify TXT record" button, all 3 domain changed into "TXT record found", and the first domain proceed to be stuck at "Adding federated domain".

Looking into the HCW log (always a good place to start with %appdata%\Roaming\Microsoft\Exchange Hybrid Configuration\), the following error was found:

2017.04.20 01:08:12.023 *ERROR* [Client=UX, Page=DomainProof, Thread=17] Microsoft.Online.CSE.Hybrid.Provider.PowerShell.PowerShellInvokeException: PowerShell failed to invoke 'Set-FederatedOrganizationIdentifier': Unable to reserve domain "FYDIBOHF25SPDLT.company.com" for Application Identifier "000000004C04A704".  Detailed information: "A Windows Live ID error occurred. Detailed information: "PassportError: Passport error.".". ---> System.Management.Automation.RemoteException: Unable to reserve domain "FYDIBOHF25SPDLT.company.com" for Application Identifier "000000004C04A704".  Detailed information: "A Windows Live ID error occurred. Detailed information: "PassportError: Passport error.".".

                                   --- End of inner exception stack trace ---

                                   at Microsoft.Online.CSE.Hybrid.PowerShell.RemotePowershellSession.RunCommandInternal(Cmdlet cmdlet, SessionParameters parameters, Int32 millisecondsTimeout, PowerShellRetrySettings retrySettings, Boolean skipCmdletLogging)

                                   at Microsoft.Online.CSE.Hybrid.Session.PowerShellOnPremisesSession.SetFederatedOrganizationIdentifier(SmtpDomain accountNamespace, String delegationTrustLink, SmtpDomain defaultDomain)

                                   at Microsoft.Online.CSE.Hybrid.App.ViewModel.Pages.DomainProof.DomainInfo.AddFederatedDomain(IOnPremisesSession session, AppData appData)

                                   at System.Collections.Generic.List`1.ForEach(Action`1 action)

                                   at Microsoft.Online.CSE.Hybrid.App.ViewModel.Pages.DomainProof.VerifyActivity(IOnPremisesSession session, IEnvironment environment)

Restarting HCW did not help.

Resolution: Verify one domain at a time. In the page "Select the domains that you want to be part of your Hybrid Configuration", pick only one domain, and click Next, and proceed to verify that domain. Using the Back button, go back and pick another one (and unselecting the previous one) and verify that domain, and repeat for the last domain.

Hope this helps someone.