Can't reply to emails using Moto X

[MLRyan]

I have a new Moto X. My gmail account has two other email accounts forwarded to it (an msn account and another from a website I manage). I receive the messages from those accounts on gmail on my phone, but when I try to reply or forward those emails, I get a failure message. Any idea how to make this work? Thanks!

 

[Rukbat]

Check the headers in a real email app. Is the email being sent to the recipient, or is it being forwarded by gmail to the recipient (which won't work)?