As it pertains to e-mail systems and electronic communications, United States law is basically straightforward: you can generally monitor communications on your own network provided you tell users what your monitoring policy is, and government agencies can generally monitor your networks, either with your permission or after obtaining a search warrant . Access by third parties that are not the government will depend on the facts of each case. Many of the finer points, however, are still open to interpretation. Accordingly, it s a very good idea for you to get your company s legal department involved in any matter that requires you to monitor mail, allow access to someone s mailbox without their knowledge, or comply with a government order.