Who owns the contents of a personal letter that I receive?
All the letters you write are copyrighted. However, letters are not, unless previously agreed, secret. You may report on what letters you are sent, and reveal what it says. If the message has no copyright notice and no commercial value, a person would be unlikely to recover damages for revealing its truthful content, but if you want to stay strictly in the law, you should ask first. Note as well that, the law aside, keeping private correspondence private is a courtesy one should usually honor.