There are some exceptions here... All technical things. Not sure about the LEGAL issues with email though.
But, an unencrypted message, full of (literally) out right LIES, with about 6 people who had no business being involved in the CC field... Yeah, you are hosed, buddy.
Legally, well, it depends who is asking. And you are right, it can be private if it is encrypted. However, as a practical matter there's a chance, always, that a) someone will forward it, intentionally or not, to someone who is not supposed to see it or b) that it will be subject to discovery under some set of facts (which means, actually, that you could be ordered to decrypt it). So we tell our clients, and each other, NEVER assume your e-mail is private. Even if its privileged, there's still a chance that its not private. I've done some discovery where I've read e-mails that, believe me, no one ever thought anyone else would read, let alone a young lawyer with a cup of Starbucks in a back office. And I was the least undesirable person reading it . . . after all, I'm with the defense . . . .
Edit: Also, there's a circuit split on whether the laws regarding private communication (like snail mail) apply to e-mail if its on an external server. I'm going from memory, but I'm almost certain at least one of the Circuit Courts has found that no warrant is needed to look at your e-mail.