Dear all, I ma having serious problems getting Exchange to look up free/busy information cross-forest.

The scenario is this:

A free/busy Component server has been set up between Exchange and a different mail system. Locally on the free/busy component server the lookups to the other mailsystem works fine, so I know this is not the cause of the issue.

To allow for the Exchange system to do its lookups, an availabilityaddressspace is added for the other system, pointing to the URL of the free/busy component server (TargetAutodiscoverEpr) and the URL has been verified working from the Exchange server.

The Remote users are added in Exchange as mailcontacts with a targetaddress that belongs to the other system, and another component is used to route mail to it. This works perfectly, so no issues with the mailrouting either.

When I try to book a meeting with a user on the other system, I get an error in Outlook 2010 (with Diagnostics enabled) that says: Unable to send cross-forest request for mailbox <Displayname>SMTP:name.lastname@domain.com because of invalid configuration., inner exception: Microsoft.Exchange.InfoWorker.Common.Availability.AddressSpaceNotFoundException: Configuration information for forest/domain domain.com could not be found in Active Directory.

I am really wondering what I am missing in Exchange that prevents it from looking up the information from Active Directory, or what exactly is missing. The thing is, this system has been installed exactly like other systems in the same organization and the other locations are working fine. I have narrowed it down to having something to do with this exact Exchange installation.

Any ideas?

Hi,

Generally, in Exchange server, the user needs to use Autodiscover service and Availability service (EWS) to retrieve the free/busy information from other users within the forest or cross forest.

Therefore, if the Exchange users send cross-forest free/busy request to the free/busy Component server or the different mail system, the EWS external URLs should be available and configured correctly for accessing. I am not familiar with how your free/busy Component server retrieve free/busy information between Exchange and the different mail system. So it cant be determined the issue is caused by the wrong configuration in Exchange server or your component server.

For your reference, the following article is the general configuration about Cross-Forest Free/Busy in Untrusted Forests between two Exchange servers:

http://blogs.technet.com/b/msukucc/archive/2013/11/27/cross-forest-free-busy-in-untrusted-forests.aspx

Hope it would be also helpful in your scenario.

Best Regards,

Winnie