Secure email for Indian government officials

India wants secure email for 50 lakh government employees. Reference. It is a good idea. But how to make Indian government emails secure? The revelations of Edward Snowden prove that USA can spy on any email and USA has the power to switch of Internet. So make India's emails secure

• Only open source Operating System like GNU/Linux should be used. If Microsoft's Windows Server is used for emails, then USA can easily coerce Microsoft for back-door access to emails.
• The servers should reside in India at multiple locations for redundancy.
• When one Indian official sends email to another, the data should NOT go to destiantion via another country like USA, for that would be a security breach.
• Even if USA activates the Internet kill switch, Indian networks should continue functioning.

For emails, it is easy to come up with an unsecure disaster-prone solution. Designing a secure, disaster-redundant solution will take more time and effort, but it would be worth it.