There is in fact no evidence that the government (any government) is "reading all our emails", or has had the access to do that. There is, on the other hand, a virulent conspiracy theory that the PRISM disclosures from Snowden revealed NSA's ability to do that; that claim was so false that Greenwald now (somewhat deceptively) denies he even acknowledged it.
That would be targeted to individual(s) not "all email from everyone" NSLs target a service or an individual or a corporation. Bad as that is, it's not intercepting, storing, scanning every email.
I suppose it's how you choose to interpret other people. They may not read everyone's email, but they certainly can read anyone's. This was always the scary part to me.
