We are migrating and Exchange 2003 server to 2010. The 2010 CAS array consists of two servers. We tried to switch external name, webmail.contoso.com, from the current 2003 OWA server to the 2010 CAS array. Outlook Web Access worked perfectly. We tried OWA from Windows 7, Windows 8, Mac, Windows Server 2008 R2, and Windows server 2012 R2. All worked perfectly.
The problem we ran into was the smartphones. None of the smartphones would sync. We tried setting up new accounts on smartphones. We were not able to setup the accounts on the phones. We got an account error. We tried many more times the password lockout policy would allow and none of the accounts were locked out so I think the requests aren't even reaching the domain controllers.
Thanks for your help.