Recently, my client acquired one small organization (14K mailboxes), and they having Exchange 2010 environment and customer environment also exchange 2010. So I was part of the M&A activities. One of the critical task is configure free/busy across the forest. But creating trust between two forest is much easier.
Below is the scenarioWhen target Forest resolves the Source domain for Free/busy it should resolve “Autodiscover.Source.com” to your source forest client access server.
I try to do test email auto configuration from Target.Com, Source.com in to a mail contact "firstname.lastname@example.org"
Also you can observe "Autodiscover.Source.Com" resolves through DNS to the source forest client access server.
In our case , we have Configured DNS forwarders from Target DNS server Forwarding my unfulfilled requests to Source DNS server,Where I have a HOST A record in the source domain already “Autodiscover.source.com” Resolving to our source Exchange Client access server
Once it is complete, we introduced FIM for GALSync from source to target forest, and now you got to add your AvailabilityAddressSpace on the source forest
Run the Below Command on the Source Forest
Add-AvailabilityAddressSpace -ForestName Target.com -AccessMethod PerUserFB -UseServiceAccount $true
Giving "ms-exch-epi-token-serialization" permission to the Source Exchange Servers over the Target Forest
Run the Below Command on the Target Forest
Get-ClientAccessServer | Add-AdPermission -AccessRights ExtendedRight -ExtendedRights "ms-exch-epi-token-serialization" -User "Source.com\Exchange Servers"
Run this command in the Source forest to export the SCP from the Source forest to the Target forest
So that the Target forest will have the Free busy information of the Source forest
Save the Credentials of the Target forest.
Please Type “DomainName\Username” and Password
Export-AutodiscoverConfig -TargetForestDomainController "Targetdc.target.com" -TargetForestCredential $Target -MultipleExchangeDeployments $true
Now Autodiscover information has been Exported from from source forest(Source.Com) to the Target forest (Target.com)
Now we are able to use autodiscover & Access free busy without any issues.