[Exim] Adding a disclaimer to out going emails

Can anyone tell me if there is a way to get exim to add a corporate
'disclaimer' to the end of outgoing emails?

The server that exim run on is a central hub with no local users, there
are various lookups that determine if the email passing through is inbound
or not. Anything going out is passed to a single router so I guess that
something in there (or a custom transport used only by that router) would be
the place to put it but I'm not sure exactly how to do it. Has anyone done
this? Any suggestions would be welcome.

Thanks,
Ian Marsh

IT Services,
Hampshire County Council