How is Zoho Mail Secure?

I read in the news recently that Zoho Mail is a major problem for the NSA, so I wondered how is Zoho Mail secure.

For instance: http://ift.tt/1ER6W9J

Why is it more secure that the other mail providers?

And how can we be sure it is truely secure since it is hosted in the USA (according to http://ift.tt/1xeKG4o)?