I am getting the following error

Sending error 550 - reverse path not authenticated user (#5.7.1) Your message has been saved in drafts.

I have a couple different email accounts set up to send email to my mailblocks account. I check my mailblocks account through chatteremail. I get this message when I try and forward the emails. What must be happening is that the mail I am trying to forward was sent to and I am trying to forward using my mailblocks account. Am not sure how to get around this.