This is a good capsule summary of the situation, with a peculiar set of conclusions. If, as you assert without anything better than the analogy with the telephone to support you, the Fourth Amendment itself should be the only legal standard for judging email searches, why isn't the rule the same one that attaches to other "important," "vital," or "critical" documents and information in the hands of unaffiliated third parties, namely that no warrant is necessary and the government can do what it needs or wants to do using subpoenas?

The statute was designed to provide more than the Fourth Amendment would provide, and it does so. People have responded to the blandishments of the world's largest intelligence service, however, and have decided to store all their personal communications forever on computers belonging to unaffiliated third parties who offer them "free" email services in return for being allowed to spy on their communications, and—oh so coincidentally—also rendering those communications easily subject to subpoena by government, which then begins eroding as much of the statute's remaining protections as they can.

A better solution is for everyone to have an extremely cheap, simple appliance that stores all their email in their homes and makes it accessible to them via their mobile devices everywhere. That email would then be reachable only by search warrant, both before delivery by any ECS storing and forwarding the mail for delivery, under ECPA, and at the residence, under the Fourth Amendment. The statute would do what it was intended to do, and everyone would be fine.

Of course, even without such an appliance, running a personal mail server is trivial for those with knowledge and even scant resources. And for everyone, without exception, Google Mail represents a loss of liberty that's far more expensive than the cost being saved by "free" service. But blaming ECPA for the peoples' bamboozlement and failure to protect their rights seems to me an odd outcome. I may well be wrong, but the arguments you would need to make in order to explain why aren't touched on here.