If you have multiple GALs (Virtual Organizations) in the environment and its been segregated using address book policies. GAL1 user can view the information residing contact cards of the GAL2 user. To avoid that
you can configure the ABP Routing Agent, If that level of separation is not required . you can safely skip these process.
When the ABP Routing agent is installed and configured, users that are assigned to different GALs appear as external recipients and they can’t view external recipients’ contact cards.
Open Exchange Management shell –
Install-TransportAgent -Name "ABP Routing Agent" -TransportAgentFactory "Microsoft.Exchange.Transport.Agent.AddressBookPolicyRoutingAgent.AddressBookPolicyRoutingAgentFactory" -AssemblyPath $env:ExchangeInstallPath\TransportRoles\agents\AddressBookPolicyRoutingAgent\Microsoft.Exchange.Transport.Agent.AddressBookPolicyRoutingAgent.dll
Enable-TransportAgent "ABP Routing Agent"
or Start – Run – Services.msc
You can run below to check the agent has been created.
Set-TransportConfig -AddressBookPolicyRoutingEnabled $true
Now other GAL users can’t view their other GAL users contact cards.