In the course of re-reading the opinion to post it, I recognized that I was misreading a key part of the opinion. As I read it now, Judge Mosman does not conclude that e-mails are not protected by the Fourth Amendment. Rather, he assumes for the sake of argument that the e-mails are protected (see bottom of page 12), but then concludes that the third party context negates an argument for Fourth Amendment notice to the subscribers. I missed this because the reasoning closely resembles the argument for saying that the Fourth Amendment doesn’t apply at all, and I didn’t read the earlier section closely enough. That’s obviously a much narrower position, and I apologize for misunderstanding it the first time in the quick skim I gave it. Sorry about that: The fault is entirely mine.