Getting mail to send with the same address...

I have about 5 different email addresses and I'm trying to figure out just how to get the mail app on my macbook air to send a reply with the same address the original email was sent to. It seems like it always wants to change it and send it with the @me account instead of the one that received it. I've gone into Preferences and checked "use only this server" but that doesn't seem to fix this particular problem.

Any ideas or thoughts?