Your bounce-back to the reply can simply be to redirect the user to the proper channels of support based on their specific request.
If a customer needs support, you don't want them pulling up that last "offer" email they received and trying to get help with a technical problem. From a company perspective, you would lose control.
Just bounce back 2 links:
1) Click here for sales.
2) Click here for support.
I am not attacking you but your argument. What decade are we living in? The 1960s? Why must I sort my question into the correct category before choosing an emal address for the company?
Email filtering and classification software can and should handle this with aplomb. Is there any argument whatsoever that existing technology can't classify questions by email in such a constrained problem space?
The point here is that the company can and should handle responses and figure out how to route them in a cost-effective manner, not throw up roadblocks in the form of links to click or multiple email addresses to use to post a question.
One way or another, it's worth trying to get these e-mails into your support channel.