UPDATE 2-INSIGHT-Microsoft failed to warn victims of Chinese email hack--former employees

SAN FRANCISCO, Dec 30 (Reuters) - Microsoft Corp experts concluded several years ago that Chinese authorities had hacked into more than a thousand Hotmail email accounts, targeting international leaders of China's Tibetan and Uighur minorities in particular - but it decided not to tell the victims, allowing the hackers to continue their campaign, according to former employees of the company.