Reading is not copyright violation (+ more!)
@ Lewis Mettler 1:
re: "Generally both the sender and receiver of a letter is priviledged to do with the content as they desire.
Simply put that means that when you receive a letter or email you can republish the contents if you so desire. Or, to put it another way, the sender does not have exclusive control over the contents of the letter. If you do not trust the other person then do not share your thoughts with them. It is pretty simply."
In the US, at least, that's simply not correct.
Copyright does not prohibit reading (where the extent of "use" is reading the content); COPY right is a bundle of rights which do prohibit COPYing and a large swath of republication uses (fair use exceptions might apply, such as libraries and academic research).
The author of a work (a letter is a work under copyright law) does not lose ownership of the copyright to that work merely by sending it to somebody else. While ownership of the work passes to the recipient upon delivery, copyright (unless explicitly assigned to another) stays with the original content author (and, upon death, the estate/spouse/children).
Don't confuse ownership of the object with copyright to the content.
Nor does publication by the author (e.g., on the Web) result in the loss of copyright (the faulty premise behind the recent cooking website owner who claimed it was okay to publish articles found on the internet because she honestly believes anything found on the Web is public domain).
And don't confuse privacy with copyright.
Many in this thread fail to recognize a right to privacy or secure communications (one can engage in private communications, if protective measures are used or sometimes merely claimed, such as proper notices of confidentiality) is not the same right as copyright.
Privacy raises an entirely different set of issues.
Besides the requirement that measures to employed to maintain privacy, another requirement is that there be a reasonable expectation of privacy. It's unlikely a court would find a reasonable expectation that a mail service would not read email (but for specific prohibition of electronic communications legislation or privacy laws, or possibly terms of service or contract restrictions). So then the privacy claim analysis heads in those directions--but does not follow a copyright analysis.
Copyright does not prohibit reading the content. It violates no copyright for Google to scan (or even read) the content, and then to use the content (without publishing the content) to do other stuff. Copyright restricts some uses of a protected work, but not reading. Copyright is not a simple concept with common knowledge application.