How do I get the mailer daemon failure to stop when I'm forwarding and editing a(n) email I already have?

I'm taking a pre-existing email and cleaning it up, then I'm taking that email and forwarding it to myself. I've been doing it in the past and now it's giving me the mailer daemon failure message when I wasn't getting it in the past. What's going on?
How do I get the mailer daemon failure to stop when I'm forwarding and editing a(n) email I already have?
You are either typing in the email wrong.... or that persons email has been deleted by them. ( or other people)
meaning of names