Note: To ensure that you see more up to date guidance related to this scenario, please see this blog post.Organizations often need to share availability (aka Free/Busy) information with other Exchange organizations. Depending on the version of Exchange Server you're on, there are different ways to do this. Let's take a look at three common scenarios and go through the exact steps required in order to achieve sharing of availability information between two on-premises Exchange organizations. Scenarios:
|Exchange Version present in Source organization|
|Required Components||Exchange 2003/2010||Exchange 2003/2007/2010||Exchange 2007/2010||Exchange 2010|
|Federation Trust/ Organization Relationship||X||X||X||X|
|Availability Address Space||-||X||X||-|
|Public Folder Database on 2010 Sp1 with Replicas of some/all Free/Busy folders*||X||X||--|
Note: Directory synchronization is not required in order to do cross-org availability in Exchange 2010 SP1, except if you have users on Outlook 2007/2003. However, if you choose to configure directory synchronization, it'll not impact the ability to perform availability lookups.directory synchronization is requiredbetween the two organizations. You must also create an availability address space for the remote organization. This allows Exchange 2007 users in both organizations to benefit from Exchange 2010's support for federation.
Add-AvailabilityAddressSpace -AccessMethod InternalProxy -ProxyUrl https://Exchange2010SP1CAS.InternalDomain.com/ews/exchange.asmx -ForestName Fabrikam.com -UseServiceAccount $TrueWith this setting, when an Exchange 2007 user requests availability information for a user from the remote org, the request will be proxied through the Exchange 2010 Sp1 server, which then will utilize the Federation Trust and Organization Relationship to send the availability request to the remote forest availability endpoint.
Set-organizationrelationship –identity “Org Relationship name” –TargetSharingEPR https://outlook.contoso.com/ews/exchange.asmx/wssecurity
Note: the actual URL that you use will differ from the example above. You can determine the URL by checking the ExternalURL property for your Web Services virtual directory. This can be obtained by running Get-WebServicesVirtualDirectory –server 2010cas.contoso.com | fl name, *url*Figure 2: Exchange 2003 user requests availability information for user in remote org (Option A)
Note:This External free busy folder will only be created on a new Exchange 2010 SP1 install when the option to create the public folders is selected during setup. The option is only presented if it's the first server installed in the organization. If a public folder database was not created during setup, you'll need to manually create this folder. The process to create this External folder is simple.
This will create the new Schedule Plus free busy folder called "External (FYDIBOHF25SPDLT)".
Set-OrganizationRelationship –Identity “Org Relationship name” –TargetSharingEPR https://outlook.contoso.com/ews/exchange.asmx/wssecurity
Note: the actual URL that you use will differ from the example above. You can determine the URL by checking the ExternalURL property for your Web Services virtual directory. You can obtain it by running Get-WebServicesVirtualDirectory –Server 2010cas.contoso.com | fl Name, *url*
<add key="maximumQueryIntervalDays" value="62" />
Note: The maximumQueryIntervalDays value is not present by default. If this value is not present, Exchange uses the default interval of 42 days.After you do this, you will want to do an IISReset on the Exchange 2007 CAS servers to make sure the new setting takes effect, as this value is only read on startup.
Set-OrganizationRelationship –identity -targetSharingEPR https://mail.contoso.com/ews/exchange.asmx/WSSecurity
Update: The issue has been fixed in Exchange 2010 SP1 Update Rollup 4. See KB 2506820. The free/busy information does not display of a user whose mailbox is located on an Exchange Server 2003 server.
An additional issue with queries for remote Exchange 2003 users is that the remote organization will return the Free/Busy response in the format of a MergedOnly string. Exchange 2010 cannot convert this string to store the result in public folders, so no information is returned to the Outlook client. A fix is available for this issue. See KB 2567863 Free/Busy information may not be returned when a Cross-Org query is performed from a legacy Exchange user.
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