ListServ 1.8e with LSMTP 1.1b on W2KSP4+latest patches

I got a bounce back from a remote system.  A user at that system tried to
sub to a list, and the confirmation message from my Listserv box is what
bounced.  I got the following:

Your message did not reach some or all of the intended recipients.

      Subject:  Command confirmation request (F63FBA04)
      Sent:     10/5/2003 8:54 PM

The following recipient(s) could not be reached:

      [log in to unmask] on 10/6/2003 10:43 AM
            The message contains a content type that is not supported
            <spaminator1.munged.com #5.6.1 smtp;554 5.6.1 Body type not
supported by Remote Host>

A quick Google search on this error shows that the remote box doesn't accept
8Bit MIME, and most of the hits were about Exchange and Postfix.

My questions:
1) can someone confirm where the problem lies?  Is the remote system not
accepting something that one normally should?  Or is my system sending
something that one normally should not?
2) Assuming the latter, what change should I make?

I can provide additional config info if needed, but as a start, here's what
I think is an applicable line from my list config:
Language= NOHTML,EXCHANGE

Thanks in advance,