It is also wise to never open an attachment that you receive from someone that you don't know. Computer virus can be very dangerous and render your computer useless. You should have a virus scanner, and always be leery of an e-mail attachment that you haven't been expecting. Harassment - Sometimes people can get upset and have disagreements while chatting or posting messages on bulletin boards. This can sometimes lead to harassment via e-mail.
Nobody likes to be harassed in any way, and it's just as illegal on the internet as it is otherwise.
If someone is harassing you through e-mail, the best thing to do is take steps to prevent it from happening again. Be cautious of your online habits. Don't give out your e-mail address freely, or post it on bulletin boards. Avoid posting too much personal information about yourself on public profiles, or chat rooms. If you are being harassed or threatened, don't delete any messages that you receive from the harassor as this is evidence against them.