One of the list owners on my server received a rejected posting message 
even though she didn't send anything. When I examined the message 
headers (partially included below) I noticed that it appears as if a mail 
relay (see the Received lines for the eSafe SMTP Relay) bounced a 
previous message back to the list. Listserv had accepted the headers as 
legitimate, but didn't post since that message had already been posted.

Has anyone else had a similar problem? Considering that this is a potential
mail loop, even though it has only occurred once, so far, what is the best
way to protect my list server from being involved in this sort of loop or from
being used as an outlet for spammers? The list involved has Send=Editor,Hold
in its header file and the bounced header in the message included a valid
Approved-By and From lines.

Andrew

== Included headers ==

Return-Path: <[log in to unmask]>
Received: from 198.51.228.229 by LISTSERV.ELCA.ORG (SMTPL release 1.0d) with TCP; Thu, 21 Dec 2000 08:12:38 -0600
Received: through eSafe SMTP Relay 977407782; Thu Dec 21 08:16:16 2000
Received: from PickupDirectory by hntbw20.hntb.org with SMTP (Microsoft Exchange Internet Mail Service Version 5.5.2650.21)
        id ZKYQSS6S; Thu, 21 Dec 2000 08:13:46 -0600
Received: through eSafe SMTP Relay 977389724; Thu Dec 21 03:08:56 2000
Received: from elca10 ([205.138.172.21]) by elca8.elca.org  with Microsoft SMTPSVC(5.5.1877.197.19);
         Thu, 21 Dec 2000 03:00:17 -0600
Received: from LISTSERV.ELCA.ORG by LISTSERV.ELCA.ORG (LISTSERV-TCP/IP release
          1.8d) with spool id 4564 for [log in to unmask]; Thu, 21 Dec
          2000 03:00:29 -0600
Received: from 205.138.172.23 by LISTSERV.ELCA.ORG (SMTPL release 1.0d) with
          TCP; Thu, 21 Dec 2000 03:00:24 -0600
Received: from mail pickup service by elca8.elca.org with Microsoft SMTPSVC;
          Thu, 21 Dec 2000 03:00:02 -0600