[OT ish] converting charsets

[Ulysees]

Running 4.25-14 with sendmail on Fedora passing through to exchange and I've
been getting a few funky messages & I'm not sure if it's the MTA or
mailscanner that's to blame

Mails come through to the exchange box with the following message:

This message uses a character set that is not supported by the Internet
Service. To view the original message content, open the attached message.
If the text doesn't display correctly, save the attachment to disk, and then
open it using a viewer that can display the original character set.
<<message.txt>>

 message.txt appears to be the actual email + headers
interesting bit is below, any ideas ?

Content-Type: text/plain; charset=unknown-8bit
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by
mailscanner.ulysees.com id i0S9MQxp027610