When do you use the forward in an email?
normal forward means, someone send you a massage and you can send the exact massage to someone else, which also includes, all the recipients who got the mail so far.
Auto forwarding is, say u have 2 email accounts. then u just want to check 1 mail account, so on the other email, u do the auto forward , so your massage will be automatically forwarded to the 1st email account.
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.