The only messages that result in auto-deletion of the member contain
 things like,
 
 --> Error description:
 Error-For:  [log in to unmask]
 Alias:      [log in to unmask]
 Error-Code: 3
 Error-Text: No such local user.
 
 in the body of the mail message.  There also has to be a line in the
 mail header that triggers the code in LISTSERV to look for that info.
 So, while human mail reading machines :) can tell that any note that
 says "Invalid userid" is a dead e-mail address, LISTSERV won't remove
 the subscriber unless the note is in a specific form.  It could be
 that the mail rejections your list owner is seeing aren't being
 generated by a system that uses the format LISTSERV recognizes.  If
 you'd like to test that theory, try adding an address to the list in
 question that is on a system that runs LMAIL or PMDF (I don't know
 what version of of PMDF is required).  If LISTSERV removes the address
 when the delivery error is received then your server is working fine.
 
 -jj
 
 PS - There may very well be other software packages that generate
 LISTSERV-edible delivery errors (MX perhaps?).  I just mentioned
 LMAIL and PMDF because I'm aware that they do so.