Many Thanks LiFePo4 for your comprehensive answer.
Although this could be related only with the old EAS2003 (not clear to me, still), it does NOT happen before with the previous WP7.0 or WM6.5 and ALL the competition like Android, iOs, etc. seems not to have reported ANY problems.
IMHO to Microsoft: please think on your mobile Customers of your corporate applications. This issue above and not been able to directly sync with Outlook are making many of us thinking not to migrate into WP7.5, again! (I’m currently still using WM6.5, after checked that WP7.0 was not good enough!) and starting pondering other mobile platforms. PATIENCE HAS A LIMIT!!!