I'm not going to act like I know the conclusive answer because there are too many factors to consider here, but one thing you may want to ask yourself is, do you do any work at home? If you do, then it is less likely that you have a "reasonable expectation of privacy."
If you were terminated, talk to an employment law attorney. If you are in trouble with the law, talk to a criminal defense attorney.
This is not legal advice: it is intended to be used for general informational or educational purposes only. For a free case evaluation, visit FairfaxCountyCriminalDefense.com.
I agree with Atty. Vincenzes. If you do any work from home, and thus operate thru the employer's server, you likely have no privacy any more than you would on an office computer. I have little knowledge of the tactics of hacking, but if all they do is pay a bill, and your online activity at home is off the company's server, your likelihood of privacy is much better. I would not share a PO Box. I think anyone has the right to open mail correctly delivered to their address.
To questioners from West Virginia & New York: Although I am licensed to practice in your state (in WV, on inactive status as of 9/13), I practice on a day-to-day basis in Massachusetts. I answer questions in your state in areas of the law in which I practice, and in which I feel comfortable trying to offer you assistance based on my knowledge of specific statutes in your state and/or general principles applicable in all states. It is always best, however, to work with attorneys and court personnel in your own area to deal with specific problems and factual situations.