[arch-general] Mutt client-Message from Gateway

Dear list, as some of you strongly advise me, I finally set up Mutt as my mail client. I set up with a gmail account, offlineimap and msmtp. Even if I don't maximise the beast, everything works fine. I still have one issue when sending or replying to this list. After my sent, I recieved immediatly a mail FROM: Gateway SUBJECT: NDN BODY : Your message couldn't be delivered to: kingeryj,Firstclass(The name was not found on the remote site). Any idea what could be wrong in my configuration? Or maybe just an invalid adress in the list? Thank You for help. Regards