And yet you enjoy no 4th Amendment protections for parcels you send by a private carrier such as UPS or FedEx. They can snoop in your stuff all the want and it would be at most a civil matter (with rare exceptions).
Your analogy would make better sense if you were talking about using a government-provided email service. But trust me, you don't want to do that, at least if it's anything like my government-provided work email.
Substituting the postal service with private carrier services, the point still stands. People just not expect their correspondence to be peeked into, no matter how technically easy is that.
When you have a conversation in a busy mall, you have no expectation of privacy. When you communicate one on one in confines of private apartment, your speech isn't meant for others to be heard, even if that would be laughably easy to eavesdrop for a government agency.
It's not really a technicality we are arguing about but very basic expectations from a communication medium. If I write an email to my wife I don't expect it to be exposed to arbitrary strangers, although I understand that it's not as secure media as say diplomatic cables cough.
I agree that people expect discretion from their couriers (electronic or otherwise), but I wasn't talking about technical limitations this time. Privacy is something that encompasses even more than government.
The 4th Amendment is specifically a limitation on government power to compel unreasonable search or seizures. That's why I said having a private courier give up your information (not at the demand of the government) would be at best a civil matter such as breach of contract.
Now does FedEx and UPS routinely give up our parcels to the wrong party? No, but the reason isn't the 4th Amendment. The reason they try to deliver to the right party is because of the incredible market reaction that would occur if they were known to be routinely diverting deliveries or snooping.
But your expectation of privacy in general (as opposed to privacy against government interception) does not have any backing in law AFAIK (sadly), which is what I think rayiner was pointing out. From the perspective of the law, if you're willing to disclose information to some "random" third-party then why wouldn't you be willing to disclose it to anyone else (incl. the government)?
I agree that we should be able to expect privacy even in these cases, as it seems like a fairly large loophole if rayiner is right, especially in a world that is far advanced from the days where long-distance communications of any sort required government services and so privacy really did mostly mean "privacy from government".
Your analogy would make better sense if you were talking about using a government-provided email service. But trust me, you don't want to do that, at least if it's anything like my government-provided work email.