Good evening, Is it okay to run setup /pl after initially installing only Exchange 2010 servers in a new forest and then deciding that I do in fact need to install an Exchange 2003 server in that same forest. Will the legacy perpmissions be applied correctly, will interoperarbility between Exchange 2010 and Exchange 2003 work or will I need to correct things afterwards? Non-Microosft please comment only if you have specifally run into this same situation and put in an effort to make it work. Microsoft please comment with the answer from a member of the Exchange team. The domain is too far down the road to have to start out again so I would to make this work but if it isnt possible then I need to change course now. Thank you. IPack

You cannot install Exchange 2003 servers in a forest that only has 2010 servers in it. Please read this link: http://technet.microsoft.com/en-us/magazine/ff394355.aspx Tim Harrington | MVP: Lync | MCITP: EMA 2007/2010, Lync 2010, MCTS: OCS | Blog: http://HowDoUC.blogspot.com | Twitter: @twharrington

Hello Yes i agree with Tim you cannot install the legacy exchange in existing Exchange 2010 topology because its now considered a pure Exchange 2010 organization.Thanks Mouzzam Hussain Visit to my Blog mouzzamh.wordpress.com

I understand what the Microsoft document says but it doesnt mean it is absolute. The question, can setup /pl be run after the fact and then an Exchange 2003 box installed later, was really meant for people that have attempted to overcome this whether they succeeded or not. I am sure that a Microsoft engineer has tried, probably even the devleopers themselves, at a minimum to debug code. I suspect that there is a method to do this but that it is too complex for Microsoft to feel comfortable putting the process in black and white. That is the process I am looking for because I really dont want to uninstall the Exchange 2010 servers and start over. The problem is that I need to interoperate with and then migrate a non-DNS compliant Exchange 2003 domain and I have not found a good way to do that with a pure Exchange 2010 environment. If it exists, I am looking for that complex process that might not be mainstream at this time. IPack

Hello IPack, If this is a pure Exchange 2010 environment, you cannot deploy new Exchange 2003 Servers into the organization. on this occasion, AD schema has updated for Exchange 2010, it cannot brought back. If the Exchange organization had Exchange 2003 servers deployed prior to the deployment of Exchange 2010 and at least one Exchange 2003 server still exists in the organization, you will be able to install new Exchange 2003 Servers into the organization at a later time. Here is a related document for you: Deploying Exchange Legacy Servers into an Exchange 2010 organization http://social.technet.microsoft.com/wiki/contents/articles/deploying-exchange-legacy-servers-into-an-exchange-2010-organization.aspx Thanks, Evan Liu TechNet Subscriber Supportin forum If you have any feedback on our support, please contact tngfb@microsoft.com Evan Liu TechNet Community Support