Microsoft reached the RTM milestone for Exchange Server 2013 on October 11, 2012.
Offline support in OWA
Emails and actions are automatically synced the next time connectivity is restored.
Brings Exchange emails and SharePoint documents together.
Outlook Web App
Offers three different UI layouts optimized for desktop, slate, and phone browsers.
Ability to customize
Outlook and OWA by integrating apps from the Office marketplace. (Yes, this is a reference to the Agaves add-ins that Microsoft and partners will be making available via the new Office Store.) The new "Napa" tools and/or HTML5 are Microsoft's preferred ways to developers to build these.
Exchange Administrative Center (EAC)
Replacement of the Exchange Management Console by a Web-based Exchange Administrative Center (EAC).
Support for up to 8TB disks
And multiple databases per disk via Data Availability Group (DAG) management.
Built in basic anti-malware protection
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.").
New Data Loss Prevention (DLP)
Capabilities for identifying and protecting "sensitive data." DLP policies are based on regulatory standards, including PII and PCI. Also: new policy tips in Outlook 2013 can be set to inform users about potential policy violations.
Can be run across Exchange, SharePoint, and Lync from a single interface.
A reduction in the number of available roles to two: a Client Access Server and a Mailbox Server role.
Now integrated into Exchange 2013 managed store to provide a more consistent (across Microsoft servers) indexing and searching experience.
Inclusion of a "Managed Store"
The name of the rewritten information store processes, which are now written in C#.
Public folders are now stored in mailbox databases and can take advantage of Database Availability Groups for replication and high availability.
Data loss prevention
Capabilities that can be integrated into Transport Rules.