[Mimedefang] problems with action_add_part & rfc822

[Nick Clark]

Trying to use mimedefang (2.31) to add a disclaimer file to outgoing emails. 

Ive added a call to action_add_part in filter_end, and the disclaimer appears, which is just what I want. But, if I send a mail with a second message as an attachment, the attached message gets converted to multipart, and the message/rfc822 content type line is lost:
ie where it used to say

--=_C89784CF.1475071C
Content-Type: message/rfc822

Received: from ...

.. it now has 

X-Mailer: MIME-tools 5.411 (Entity 5.404)

This is a multi-part message in MIME format...

------------=_1048523025-27257-0
Received: from ...

And my (dumb) mail client doesnt understand that thats a message, & displays it as a strange blob thing.

Any ideas ? I can tweak the mimedefang.pl so that it doesnt create a new multipart 
in rebuild_entity, just does $out->add_part($in) but Im guessing this might be a bad thing!

Sadly, as much as I would like to not have disclaimers in mail, its not an option.

Thanks - been scratching my head all day..

Nick.