Our domain/forest is running Windows 2003 with Exchange 2003. Our sister company has its own domain/forest that runs Windows 2003 and Exchange 2007. We both plan to stay as seperate forests. We have a forest trust in place. What options are there in the following scenarios to share GAL and free/busy information? For each, I'm looking to get an understanding of the simplicity, robustness and any costs involved. I've researched each scenario and have found varying levels of detail on the possibilities but I wasn't able to get a clear pictures of it all. * We stay at Exchange 2003 and they stay at Exchange 2007 * We migrate to Exchange 2007 and they stay at Exchange 2007 * We migrate to Exchange 2010 and they stay at Exchange 2007 In a nutshell, our site is ready to migrate to a newer version and would like to migrate to 2010 for all of its new features and performance improvements but would be at least willing to consider moving to just 2007 if it'd be significantly easier/cheaper to integrate with their 2007 environment.

The InterOrg Replication Tool should work for free-busy data between any combination except Exchange 2010, for which it is unsupported. Outlook 2007 and higher use the availability service, which you can configure to connect between organizations. The following article describes the use of the Microsoft Federation Gateway for interorganizaitonal availability sharing. http://msexchangeteam.com/archive/2010/12/01/457095.aspx Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Thanks. Your information led me to finding pages that detailed out that the Availability Service could be used if we went with 2010 and ther other property stuck with 2007. Sounds like that covers free/busy data. Regarding GAL syncing this page (http://msexchangeteam.com/archive/2006/10/23/429296.aspx) says, "With Exchange 2007, organizations can use the Availability Service to provide access to free/busy data without the need of data synchronization tool (however, you still need to have directory synchronization for address list related lookups)." What options are there for GAL syncing between Exchange 2007 and 2010? The Federation setup would seem to be an option but I don't know if both sites would need to be Exchange 2010?

One option is Forefront Identity Manager. Another is to write your own scripts. There are third-party options as well. I used to have a list of them, but things have changed.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

If you don't can or want to use FIM/ILM/MIIS or scripts of your own, you can go with a 3rd part like one of those http://www.quest.com/collaboration-services/ http://www.netsec.de/en/products/galsync/Jonas Andersson MCTS: Microsoft Exchange Server 2007/2010 | MCITP: EMA 2007/2010 | MCSE/MCSA Blog: http://www.testlabs.se/blog

There's always SimpleSync, which has been around a long time too. http://www.dirwiz.com/simplesync/ And HP's LDSU, which is pricey but a very useful tool for custom situations. http://h71028.www7.hp.com/services/us/en/unified/messaging-ldap-directory-synchronizer.html Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."