When are we going to have Activesync support in K9?
K-9 uses WebDAV to communicate with Exchange. As of Exchange 2010, WebDAV is no longer supported. For this reason, K-9 is unable to work with Exchange 2010 at this time.
K-9 communicates with Exchange through and outdated and problematic protocol: WebDAV. WebDAV support is turned off by default in Exchange 2007, and completely removed in Exchange 2010. This of course implies that K-9 does not support Exchange 2010.
Exchange ActiveSync Development