On Thu, 14 Oct 1999 11:22:33 PDT, Melvin Klassen <[log in to unmask]> wrote:

>The "problem" is that when you send MIME-encoded E-mail,
>with whatever MUA that you use, MIME inserts some lines
>in the "header" of the message, to indicate that the "body"
>of the message contains various "dividers" between attachments,
>whether you send E-mail to a colleague or to the ID of a mailing-list.

These are required as part of the MIME specification.

>LISTSERV strips those lines from the headers of your message,
>and then distributes this "modified" version of your message
>to the subscribers.

Only if you have subscription options set to SHORTHDR.  This is as documented.
The normal default list settings (unless the Owner has changed them) is FULLHDR
which preserves the necessary MIME headers.