Exchange architecture revisions: Exchange 2007 and 2010 are broken into five server roles, mainly to address performance issues like CPU performance, which would suffer if Exchange were running as one monolithic application. But Microsoft has made progress on the performance side, so Exchange 2013 has just two roles: Client Access server role and Mailbox server role. The Mailbox server role includes all the typical server components (including unified messaging), and the Client Access server role handles all the authentication, redirection, and proxy services.
In-Place eDiscovery: This feature can be run across Exchange, SharePoint, and Lync from a single interface
Replacement of the Exchange Management Console: The Web-based Exchange Administrative Center (EAC). I was a little apprehensive at first using the new EAC but Microsoft did a good job of incorporating the most common admin functions. I would think the list of available functions will only increase when future service packs are released.
Site Mailboxes: Brings Exchange emails and SharePoint documents together. Site mailboxes allow users to work together naturally – while compliance is applied behind the scenes.
Modern public folders: Rather than just getting rid of public folders (something promised for future releases), Microsoft has embraced them once again. They are no longer managed through the separate Public Folder Management Console; instead, they are managed via the EAC. That makes them public folder mailboxes, which means they use regular mailbox databases. In turn, this means they can be made part of a database availability group for disaster recovery.
Built in basic anti-malware protection: the ability for administrators to configure and manage settings from inside EAC. (Note: this feature can be turned off, replaced or “paired with premium services such as Exchange Online Protection for layered protection.”)
Offline support in OWA: Emails and actions are automatically synced the next time connectivity is restored. One of the best features in the new OWA 2013 that was introduced by Microsoft is called OWA offline. OWA offline allows the user to have a full access to their mailbox even when not connected to Exchange. OWA offline behaves the same way as desktop Mic