During an Exchange 2003 to 2010 transition a legacy namespace is configured for users who are connecting to Exchange 2003 mailboxes, and the certificate must be imported on the Exchange 2003 server.
Learn how to configure an SSL certificate for Exchange Server 2010.
Your Exchange server will run for 120 days without a product key but you should enter one as soon as possible and certainly before placing the server into production.
A Typical Exchange Server 2010 is one that runs the Client Access, Hub Transport, and Mailbox server roles. This is the type of installation that would be performed in a single server organization.
Before you can deploy Exchange Server 2010 into an existing Exchange organization you must verify that your existing network environment meets the pre-requisites.