If I could have a trigger that runs when an email is sent. I think it would be relatively straightforward to set the Reply-To. (The only other way I could think of is to convert everything to Visualforce email, and that is definitely not straightforward.)
1 answer
On a per-user basis you can set a reply to in My Email Settings, but no, I can't think of any way you can intercept an email message like that.
