Yes, it's a loop.  I had the same question about a year and a half
ago.  The solution was a "one-way feed" where I subscribed the listproc
mailing list to my LISTSERV mailing list and set them to DIGEST.  Recently
it became a major pain in the a** because the people running the listproc
list didn't handle their bouncing subscribers in a timely manner, so I
deleted their subscription.  (They also did not explain the situation
to their new subscribers, so I was constantly getting "Why am I getting
these xxxxxx-L posts?")
 
Nathan