> Does anyone have any suggestions on how to implement this based on
> senders domain?
Presumably you could implement this in pure Exim with some sort of
${lookup that directs to particular transports -- I've never tried.
The [off-topic] method I chose was to use MailScanner, which we have
anyway, as I can easily avoid adding disclaimers to S/MIME messages (or
they break). I've written up a bit of how I did it at
http://blog.fupps.com/2007/05/12/mail-footers-sometimes-not/
-JP