There is a potential email problem with Windows 6.1 powered smartphones due to a new feature introduced in the latest version of the OS, and so Microsoft has released a patch to sort that problem out.
Apparently, Microsoft added a feature that would allow carriers to specify the default SMTP server for outbound mail if the user specified SMTP failed, and the problem is if the carrier doesn’t specify a default server, and the user’s specified server fails to connect, all the email account could actually be corrupted.
To gain the CAB file with the patch just point your browser at the Windows mobile download site or can also be applied by using a Microsoft Windows PC by downloading and installing the patch via the information page.
Source — mobileburn