[Exim] Is there a way to prepend lines to the body of a mail…

Hi,
I'm using
warn
message = SOMEHEADER: Some value
to add header lines from Exiscan ACLs. Now I'm wondering if there's a
possibility to also add (or more precisely, prepend) lines to the body
of a message? That would allow it to print the SpamAssassin report in
the body of the mail where the user actually sees it instead of
putting it into the header (where users obviously don't look).

Any help would greatly be appreciated.

Regards,
Gabriel