We have two separate sites with two separate forests engaged in a two way external trust. In each forest there is a separate 2003 exchange org. We would like to move to one 2010 exchange org and keep the two forests with two separate exchange 2010 servers. We have a small pipe between the two sites(400K). Can we keep one of the current exchange orgs and migrate the other mailboxes from the other org to the new Exchange 2010 org? The mailboxes at each site would stay at the same site after the upgrade to the new server.

Hi , Couple of days ago I bookmarked this link maybe it could help you. http://www.testlabs.se/blog/2010/05/24/cross-forest-migration-in-lab/ http://community.priasoft.com/blogs/exchange_migration_team_blog/archive/2010/05/20/issues-to-be-considered-while-thinking-about-moving-mailboxes-to-exchange-2010-using-the-microsoft-native-tools.aspx Regards. Shafaquat Ali. M.C.I.T.P Exchange 2007/2010, M.C.I.T.P Windows Server 2008, M.C.T.S OCS Server 2007 R2, Phone: +923008210320

Hi 2010, Per you descritpion, I would verify some infomation regarding your plan. 1. You have two site and two forest, and each forest has one exchange 2003 ORG at present, right? Do you want ot the two froest has one ORG after migration from exchange 2003 to exchange 2010? If so, you could deploy Exchange 2010 in an Exchange Resource Forest Topology, you could refer to below: http://technet.microsoft.com/en-us/library/aa998031.aspx 2. You want to deploy exchange 2010 server at each site, per my known, if so, you would have other ORG in your each site, and that is, you want to deploy Exchange 2010 in a Cross-Forest Topology, you could refer to below: http://technet.microsoft.com/en-us/library/aa998597.aspx Please confirm what topology do you want to plan. You could refer to below about how to migrate to exchange 2010: http://technet.microsoft.com/en-us/exdeploy2010/default.aspx#Home Regards! Gavin