Elm - How to specify a bounce-back email address ?

[Al Narvanen]

I have successfully used elm in a script to send multiple attachments but my problem is if the email is sent to an invalid email address, I would like the bouce-back to go to a specified email address where the undelivered email messages can be manually processed (worked off the queue).
I already have in my elmheader file; Sender: Reply-To: From: and they work fine. A receiver can select Reply and it will go to the address I specified in Reply-To:
I then added Return-path: in elmheader and sent an email to a bogus email address, but it never got bounced-back to the email I specified in the Return-path line. I do not know where it ended up.

How can I get these bounce-backs to the email address I want?

Thanks for any assistance.
Al