This has been a problem for me as well;  I have contacted tech support
about it and the official response has been:

NO mail headers of any kind in the body of the message.  I was also told
that it is a mail client problem and that I need to educate users on how
to make the client "correctly" comment a message (even with headers in
it) so that it passes through. Now, I am supporting less that 3000
users, but educating them to this change -  ie, asking them to change
their mail client for one list that they use regularly 3-5 times a week
- seems a bit extreme and probably will only make them unsubscribe; not
exactly my preferred solution to the problem. Or making them search
through an entire message from the list before they reply (for any
headers included by previous posters) could also lead them to stop using
the list.

Fortunately for me, this error only occurs 1-2 times a week out of all
the messages hitting all the lists, so I have been handling it on a
message by message basis.  This is not, the preferred way, but for me it
is working.

If anyone has a better solution, please let me know, I would appreciate
it.  


- Tim

-----Original Message-----
From: LISTSERV site administrators' forum
[mailto:[log in to unmask]] On Behalf Of Bret Hilton
Sent: Monday, February 06, 2006 9:02 AM
To: [log in to unmask]
Subject: "Sender:", "From:" or "Reply-To:" field pointing to the list
...

Dear Site Managers,

One of my list owners is asking how to deal with the following LISTSERV
error message. There appears to be some kind of safety feature in
LISTSERV that is keeping legitimate replies from making it to the list.
I looked at the 'Loopcheck' keyword, but was scared away by the doomsday
disclaimer and I'm not sure where else I should be looking.

Thanks for your help,

Bret Hilton


BEGIN LISTSERV MESSAGE:
***********************

The enclosed message, found in the [LISTNAME] mailbox and shown under
the spool ID 25545 in the system log, has  been identified as a possible
delivery error notice  for the  following reason:  "Sender:", "From:" or
"Reply-To:"  field pointing to the list has been found in mail body.