move archive-enabled mailboxes from one Exchange server to another in diferent forest

Hi 

 

My requirement is to split the organizaton from  today one forest with exchange 2010 and EV 10 creating a new forest with exchange 2010 

I have to move around 400 users ( account and exchange mailbox ) that are archive enabled to the new  forest 

is it possible to keep the archive for the moved mailboxes ? , if not what is the best solution ( export to pst files )?

 

Forest A

User accounts

Excahnge 2010

Enterprise Vault 10.0

A two way trust exist between forest A & B

 

Forest B

Exchange 2010 

user accounts