Why Don't the Legal Standards That Govern the Privacy of Letters Apply to Emails?

Should your emails have the same legal protection as your letters?

We assume the answer is yes, but the real answer is no. As the New York Times points out, the Electronic Communications Privacy Act gives law enforcement officers a much easier path to your private online life than your offline one. As a greater share of our affairs have moved to the Internet, this means that there has been a mass erosion of civil liberties sanctioned by a law passed back in 1986 when almost no one had email and the Web had yet to be invented.

For example, the Feds don't need a warrant to read emails that are more than 180 days old, whereas if you had letters in your home, they'd need a court order. Leaving aside the time element, which seems plucked from thin air, it seems impossible to justify why one mode of communication would receive greater legal protection than another. In this case, the law should not take the medium for the message.