I have few doubts regarding upgrade and coexsistance of Exchange Server 2010 with Exchange Server 2003 and sure to get the answers here. Current infrastructure:1. We have 16 AD sites across middle east and north africa with 1 Exchange Server at every site.2. Sites are connected via site to site vpn.3. It is a single domain (changing the name here) called contoso.com. There is no child domain. Windows 2003 forest level. 4. Every Windows 2003 AD has sp2 and Exchange 2003 with sp2.5. We have 6 offices in UAE, and main data center located in one of our offices in Dubai. This office has got Exchange 2003 Enterprise. All other offices have Exchange 2003 standard. We have only one Exchange 2003 Front End Server all together.6. 6 offices in UAE connect to this Front End Exchange Server for RPC over HTTP and OWA. Offices in other countries directly access their Exchange Back End Server for RPC over HTTP and OWA. I have edited the registry setting in the BAck End Servers of the remote offices to support RPC over HTTP. Proposal:1. We are planning to upgrade our messaging environment to Exchange 2010. Initially we will only upgrade the server in Dubai office (only one site) and want to co-exist with Exchange 2003 in other office. My doubts:1. Is there any known issue in co-existing. We may slowly move all other offices to Exchange 2010, but it may take 1 year.2. Will there be any problem with the GAL / Calendar free busy schedule? Can the remote office people (who are in Exchange 2003) see the calendar of people in Exchange Server 2010?4. Do I need to create a new routing group connector in all remote office to send mails to\from new Exchange Server 2010 located in head office?5. Will I be able to add Exchange 2003 server to the forest after I prepare the forest for Exchange 2010 support. I read somewhere we cannot add anymore Exchange 2007 roles.6. Will I be able to create and propagate new routing group object after editing the registry for supress link state. I dont have a lab facility to replicate our IT structure for testing. I appreciate all your time and help. Thanks a lot. Regards,Tariq

1. Shouldn't be a problem. 2. No problem. Be sure to replicate all free-busy system folders to all servers. Outlook 2007 users will want to contact the CAS's web services for free-busy. 3. 42. 4. You can do that, or you can create one to just one of the Exchange 2003 servers. That might be the preferred method if you are going to keep the main office Exchange 2003 in place for a while. 5. Why would you want to do that? Where did you read that? 6. I'm not sure of the question. If I didn't answer it in #4, please repost it with more detail.-- Ed Crowley MVP"There are seldom good technological solutions to behavioral problems.". "Tariq Samsudeen" wrote in message news:f990d5b9-69a4-45f7-9904-3028478e32cf... I have few doubts regarding upgrade and coexsistance of Exchange Server 2010 with Exchange Server 2003 and sure to get the answers here. Current infrastructure:1. We have 16 AD sites across middle east and north africa with 1 Exchange Server at every site.2. Sites are connected via site to site vpn.3. It is a single domain (changing the name here) called contoso.com. There is no child domain. Windows 2003 forest level. 4. Every Windows 2003 AD has sp2 and Exchange 2003 with sp2.5. We have 6 offices in UAE, and main data center located in one of our offices in Dubai. This office has got Exchange 2003 Enterprise. All other offices have Exchange 2003 standard. We have only one Exchange 2003 Front End Server all together.6. 6 offices in UAE connect to this Front End Exchange Server for RPC over HTTP and OWA. Offices in other countries directly access their Exchange Back End Server for RPC over HTTP and OWA. I have edited the registry setting in the BAck End Servers of the remote offices to support RPC over HTTP. Proposal:1. We are planning to upgrade our messaging environment to Exchange 2010. Initially we will only upgrade the server in Dubai office (only one site) and want to co-exist with Exchange 2003 in other office. My doubts:1. Is there any known issue in co-existing. We may slowly move all other offices to Exchange 2010, but it may take 1 year.2. Will there be any problem with the GAL / Calendar free busy schedule? Can the remote office people (who are in Exchange 2003) see the calendar of people in Exchange Server 2010?4. Do I need to create a new routing group connector in all remote office to send mails to\from new Exchange Server 2010 located in head office?5. Will I be able to add Exchange 2003 server to the forest after I prepare the forest for Exchange 2010 support. I read somewhere we cannot add anymore Exchange 2007 roles.6. Will I be able to create and propagate new routing group object after editing the registry for supress link state. I dont have a lab facility to replicate our IT structure for testing. I appreciate all your time and help. Thanks a lot. Regards,Tariq Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Thanks a lot Ed Crowley.I am clear now.Regards,Tariq