Exchange Archiving email from a decomissioned server.

I recently moved our exchange email to a hosted server off site.  During that move the vendor migrated all existing email for active users to the new server.  However we did not migrate email for old users who's accounts have been deactivated.  There have been times when for legal purposes I've had to startup the old Exchange server and retrieve old emails.

Is there an easy way to archive the old emails so they are easily accessible without having to keep the old server around.  I'd like to wipe the server and repurpose it.  This is an Exchange 2010 server I am working with.

Thanks