GALsync, Free/Busy, Exchange 2010, Outlook 2010 and Public Folders

Free/Busy information is stored in your partner's sites in a system public folder (that is normal Microsoft technology). So your partner can look up the free/busy information of all contacts which have been synchronized from your site before.

With Outlook 2003 and Exchange 2003, the client asked directly the information store to get free/busy information, which was stored in a system public folder. Microsoft changed its technology.  Exchange 2007 and Exchange 2010 provide free/busy information through a web service. The client contacts the web service; the web service accesses the mailboxes for retrieving free/busy information. So the public folder is not used any more for this.

It is more than fair to explain the methods of GALsync and how it provides you with this information.

We have to keep an eye on the different versions of the clients and of the servers. If we speak about Exchange 2010 we address only Exchange 2010 SP1. We do not support Exchange 2010 without Service Pack.

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1. Outlook 2003

Outlook 2003 only can retrieve Free/Busy information by accessing the system public folder hosting this information. If you use this version as your messaging client and if you have Exchange 2007 or Exchange 2010 SP1 as server version you only have to install a public folder database.
GALsync will do the rest of work for you.

Because Exchange 2007 and Exchange 2010 SP1 by default require an encrypted communication between MAPI client and server, you have to configure Exchange servers not to require encryption. This is done by a cmdlet on each Exchange 2010 SP1 server.
Set-RpcClientAccess -Server Exchange_server_name -EncryptionRequired $False

You can also retain the default encryption at server side and configure all Outlook 2003 clients to use encryption. This can be automated by Group Policies.

Outlook 2007 by default tries to get free/busy information by accessing a web service (the so called availability service).

In an Exchange 2003 environment there is no web service present and Outlook 2007 accesses Public Folders without further configuration.

In an Exchange 2007 or Exchange 2010 environment you must force the messaging client to get the free/busy information from public folder. This is done by setting a registry key on the machines with Outlook 2007:  

HKCU\Software\Microsoft\Office\12.0\Outlook\Options\Calendar
DWORD registry Key "UseLegacyFB"
value 1

You can distribute this registry key by GPO.

Instead of changing the client's configuration you might prefer a server solution. This solution works in Exchange 2007 and Exchange 2010 SP1 environments (Exchange 2010 without SP is not recommended for this).

The PowerShell cmdlet "Add-AvailabilityAddressSpace" forces the Availability Web Service to access public folders to retrieve free/busy information.

So the Outlook 2007 client connects to the availability server which then accesses the public folder database.

The cmdlet must be run for every domain you have imported objects from. For example, you have the SMTP domain "us.com" and you synchronized with your partner partner.com. After the sync through GALsync there will be contacts from your partner with mail addresses like jb@partner.com in your Active Directory. In your us.com-organization, you have to run this command:

Add-AvailabilityAddressSpace -ForestName partner.com -AccessMethod PublicFolder

After doing so, please restart Internet Information Server by running the iisreset command.

Result: all Outlook 2007 clients can get the free/busy information, which have been replicated by GALsync to your organization.

Outlook 2010 gets free/busy information by accessing a web service (the so called availability service).  . The regkey UseLegacyFB that you could use with Outlook 2007 is ignored by Outlook 2010, so you cannot connect to public folder to retrieve free/busy by this way.

So there is no client side solution we know. But you can use the server side solution with Add-AvailabilityAddressSpace.  In this case Outlook 2010 contacts the Availability service which accesses the public folder database.

If you have Exchange 2010 without SP we strongly recommend upgrading to SP1.