Today we will go through a major difference and enchancements in Exchange 2010 over Exchange 2007.
Exchange 2010 comes with new high availability concepts of DAG [Database Availablity Group] which incooperates features of CCR, SCR clustering on Exchange 2007 into single entity. Exchange 2010 don't use CCR, SCR terms but rather user DAG for high availability within site and for site resilence.
CAS Array In Exchange 2010, by design mapi clients now connect to the Client Access RPC service that runs on cas server. High Availability of CAS servers can be achieved with using CAS Array with load balancers. CAS Array means that we can combine all the cas servers in single site as one server to which clients will connect. Then request will automatically be proxied over to the appropriate cas servers.
Storage Groups have been removed and database are no longer associated with particular storage group or server rather they are moved to Org level.
Permission model has been resived in Exchange 2010. With Role Based Access control also spelled as RBAC, you can define extermly broad or extremely precise permissions model based on the roles of your administrators and users.
You can grant users with the rights to change their own personal information, contact information, DL group membership hence delegating most common administrative tasks to the end users itself.
Transport and Routing Functionality:
Shadow redundancy Messages that are submitted to an Exchange 2010 Hub Transport server are stored in the transport database until the next hop reports successful delivery of the message. If the next hop doesn't report successful delivery and it fails, the message is resubmitted for delivery.
Moderated transport Exchange 2010 provides an approval workflow for sending messages to recipients. When you configure a recipient for moderation, all messages sent to that recipient must go through an approval process.
End-to-end message tracking With Exchange 2010 End users are given ability to track messages.
Incremental EdgeSync In Exchange 2010, the EdgeSync process has been changed to keep track of synchronized information and only synchronize the changes since the last replication cycle. This significantly reduces network traffic and greatly improves synchronization efficiency.
Message throttling improvements In Exchange 2010, you can configure a Receive connector to monitor the rate of message submissions by users, IP addresses, or both. If you configure a Receive connector to monitor the message submission rate for users, it ensures that a specific user doesn't exceed the message rate that it's allowed, regardless of the IP address the connections are coming from. The default client Receive connector created on the Hub Transport servers is configured this way.
Mailbox and Recipient Functionality
Ability for users to share information, such as calendar free/busy information and contacts with users who reside in a different organization
Ability to move a mailbox while the end user is still accessing it
Ability to appoint a moderator to regulate the flow of messages sent to a distribution group
Messaging and Complaince
Personal Archive feature to provide users with online archive mailboxes and help eliminate .pst files
These are the major changes in Exchange 2010 over Exchange 2007. For comprehensive listing please refer to technet Artcile.