Yes.
Yes it is. As well as over your phone calls.
No, but it is not very nice - unless all your interaction with that person is by email.
depends if the persons under or over 18 if they are under a parent may but if they are over 18 they yes it is illigeal invasion of privicay.
is it illegal for someone to obtain an email that was not addresses to them?
yes
yes, it is illegal to hack into anyone's email, without their permission.
Most of the time, it is not illegal to forward email. However, there could be places, and circumstances, where it is illegal to forward email. At work, it might be illegal to forward email. It might be illegal to forward an email that has spam, or porno, or a virus in it. It all depends on where you are when you forward the email, who you forward the email to, and what the email contains.
Yes. It is illegal to make death threats in any form in all states.
NO...
Yes
no it is not illegal but is good to check first
It's not illegal to text them but if the text has anything to do regarding sex or threats etc it is illegal.