Outlook Web App is Microsoft Exchange Server 2010’s Web-based email client. Formerly known as Outlook Web Access in previous iterations of Exchange Server, Outlook Web App gives users an experience similar to Microsoft Outlook without requiring the presence of the full mail client.
Outlook Web App was revamped for Exchange Server 2010 Service Pack 1. It is now supported by all major Web browsers and includes a smoother interface. Other new features include themes, which let users customize their own personal OWA 2010 interface and calendar Web sharing, which lets users share their OWA calendars with non-Exchange users and vice versa.