Legal Question in Intellectual Property in California

The articles you've read are probably correct, especially if the writers more or less agree with each other. Caution is necessary, however, in applying academic theory to specific real-world situations. First, copyright law contains exceptions for "fair use," which is defined in numerous court decisions and which would probably include the right to copy, quote from or forward e-mail writings for normal business purposes. Second, the full force of copyright law including the right to bring suit in Federal court for infringement requires registration of a copyright. Next, bringing enforcement actions is not cheap, and unless damages can be proven against and collected from the alleged infringer, there is little incentive to sue. There might even be an issue as to whether e-mails are "creative works" so as to be subject to copyright law in the first place, but I think they probably are.

Privacy laws are quite a different matter, being very diverse in origin, jurisdiction, subject matter coverage and remedies. Nevertheless, a successful prosecution might require some of the same elements, e.g., lack of a sound reason (such as "fair use" or "privilege") and financial damages.

The writer of an e-mail is the owner of the content of the e-mail and copyright attaches automatically. Under current law, registration is not required for full copyright law protection. Even if the author does not specifically state that the e-mail is not to be copied, a recipient has no right to copy or distribute it without the author's permission. And, yes, the author/sender can bring a legal action against someone who forwards or copies the e-mail, especially if the sender has stated the e-mail is not to be forwarded. Usually such a statement should be enough, but cyberspace is full of people who care nothing for the rights of others.