Don't forward if you want to lie to the recipient that the content of
your e-mail is all your work instead of someone else's. Instead copy
the original e-mail's body and paste it into a new e-mail. That's is
don't forward but compose a new e-mail and paste into it whatever you
want. Both "Re:" and "Fw:" are well established conventions to relay to
the recipient that an e-mail is a reply or a forwarded copy of someone
else's e-mail.