set default-reply-to

SET DEFAULT-REPLY-TO [address]  -  define a REPLY-TO address for all messages

If any address is defined, it appears in a REPLY-TO field, and replies
  to your messages will go to that address.  This is equivalent to using
  the REPLY-TO command with the same address every time.

Normally, no address is defined, and the REPLY-TO field does not exist, 
  so replies go to the address the mail came from.  

To unset, type SET DEFAULT-REPLY-TO with nothing following.

For more help, type "help" and one of the following:
(at any prompt:)  save-init   set   show   
(at the Send> prompt:)  reply-to