Hi If migarting exchange server in cross forest ( one is Abc.com and other is xyz.com) should i run setup /legacyexchangepermission switch or not. Thanks Dheeraj Mishra Thanks Dheeraj Mishra MCSA+MCTS

It will run regardless whether you manually run it or not when you prep the forest for Exchange.

Why Run Setup /PrepareLegacyExchangePermissions Essentially, you must run the setup /PrepareLegacyExchangePermissions command so that the Exchange 2003 Recipient Update Service functions correctly after you update the Active Directory schema for Exchange Server 2010. This section explains the main issue and how running the command resolves this issue. http://technet.microsoft.com/en-us/library/aa997914.aspx

Why Run Setup /PrepareLegacyExchangePermissions Essentially, you must run the setup /PrepareLegacyExchangePermissions command so that the Exchange 2003 Recipient Update Service functions correctly after you update the Active Directory schema for Exchange Server 2010. This section explains the main issue and how running the command resolves this issue. http://technet.microsoft.com/en-us/library/aa997914.aspx