Amuck?  Thought it was amok.  Well, it is mucky... :-)

At 10:56 AM 2/20/98 -0500, Judith Hopkins wrote:
>Has anyone else run into this problem which one would-be subscriber sent
>to me this morning?  Our list uses CONFIRM but when he tried to subscribe
>he received nothing (or so he thought)

[snip, to user's letter]

>Hi Judith,
>
>Thanks for your help with regard to subscribing to Autocat.  As it turns
>out, I *have* actually been getting the confirmation messages, I just
>didn't know it because they have somehow been getting attached to the
>bottom of other messages -- how bizarre!  A colleague and I were discussing
>this situation yesterday, and she mentioned that she had run into a similar
>problem, and had by accident found her confirmation message at the bottom
>of another message, so I carefully checked my mail, and there it was!  I
>have forwarded to you an exact copy of the most recent message that I have
>received -- I have also gone ahead and confirmed using the other address
>and code as instructed in the message.  I suspect that this is a local
>problem, and in no way a flaw with the Autocat Listserver.

[more snip, to part of user's mailbox]

>>See you on Monday.
>>
>>Carolyn
>>
>>From  Thu Feb 19 17:42:11 1998
>>Return-Path: <Mailer-Daemon>
>>Received: from deliverance.acsu.buffalo.edu by mail.gac.peachnet.edu
>(SMI-8.6/SMI-SVR4)
>>       id RAA15104; Thu, 19 Feb 1998 17:42:08 -0500
>>Message-Id: <[log in to unmask]>

Marty was pretty close in his answer... note the line starting with
"From ".  This is the line that many mail systems use to separate mail
messages... its exact format must be agreed upon by the users's MDA
(mail delivery agent) and mail client(s) (or MUA, mail user agent).

I sent to your list for my own confirmation message, and the beginning of
it looks like this (in my mail folder):
>
>...this is where the last line of the previous mail was...
>
>From MAILER-DAEMON  Fri Feb 20 19:54:20 1998
>Received: from mailnfs0.tiac.net (mailnfs0.tiac.net [199.0.65.17])
>       by shell1.tiac.net (8.8.8/) with ESMTP id TAA00614
>       for <[log in to unmask]>; Fri, 20 Feb 1998 19:39:48 -0500 (EST)

Note that my MDA (which is sendmail) put the string MAILER-DAEMON in there,
not in a Return-Path header.  elm (a common UNIX mail client) recognizes this
as the start of a message; however, when I edited out the MAILER-DAEMON
elm believes it to be attached to the previous message.  I believe that the
commonly accepted mbox (sometimes misleadingly called "UNIX mailbox format")
delimiter is:
    "\n\nFrom " address date-and-time.
This is not an RFC; anything agreed-upon by MDA and MUA will work; however,
your user's suspicion that it is a local problem there is correct, and
specifically it looks to be his or her MDA (I don't know what SMI-8.6/SMI-SVR4
represents) isn't following the conventions required by some (many?) mail
clients when it omits the "address" part.

This problem probably occurs with all null (i.e., <>) SMTP MAIL FROM addresses;
the user can test by sending mail to a non-existent address and observing if
the resultant bounce message (which should have the <> FROM address) appears
to be attached to another mail.

Hope that helps,
Stan