> Message-Id:
>   <00A4C33A065C7009*/c=us/admd=imx/prmd=domain.name/o=co/ou=MSMail/s=LASTNAME/g=
> FirstName/i=D/@MHS>
>
> I have narrowed the problem down to the fact that his mail system folds
> (wraps to a new line) the long Message-Id: header line immediately after
> the "Message-Id:" header tag.  In the original message, that header line
> contains:
>
>  "Message-Id:" (space) (CR) (LF) (space) (space) "<00A4C33....>" (CR) (LF)
>
> LISTSERV appears to ignore all headers past this header, which includes
> the important From: and Subject: headers.  When LISTSERV distributes the
> message to the list subscribers, it indicates that the message came from
> an unknown origin, and does not provide a Subject header.

The problem is that the continuation line (starting with "FirstName")
does not begin with a space or a tab, as required by RFC 822.  So it
looks to LISTSERV like the start of a new header that is not properly
formed.