At 06:29 03/12/1999 Friday -0500, you wrote:
|One of the subscribers to the list I manage gets this line in the header of
|her digest mail:
|
|Return-Path: <owner-ZAMIR-CHAT-L*<username>**IGC*[log in to unmask]>

Looks like that is part of the updated (1.8d) PROBE feature.  Check the
List-Owner Manual -- Appendix:

http://www.lsoft.com/manuals/1.8d/owner/appendb.html#keyAutoDelete

/Pete