Hotmail limitations are caused by Microsoft. They do not have any supported APIs to access mail but WebDAV has been added using undocumented compatibility (there are a few Open Source projects). Microsoft stated quite some time ago that they would drop WebDAV support completely, but have maintained it due to Outlook Express users on Windows XP (common on netbooks).
Microsoft does have a new DeltaSync API but it must be licensed and there are no Open Source implementations. As a result, to use Zimbra Desktop with Hotmail, the best option is to upgrade to Hotmail Plus or contact their support department to see if they will enable your account without going Plus. Otherwise, the next release of Desktop will have POP3 enhancements, though that does not allow full synchronization |