Can someone give me a clue ?

["Michael Castellano a.k.a The Webmaster" <webmaster @ gcstation . net>]

I have am serving a list and it is closed, but unmoderated.
The owner just let me know that all of a sudden they have been 
getting email bounced with the sunject as follows

Subject: BOUNCE <list-name>: Admin request

The rest of the header info looks normal and they just seem to 
be normal email letters, not large in size....


Any clues would be appreciated......


Thanks in advance

Mike Castellano