Appending a footer?

Hi list,

I'm currently banging my head against the desk trying to figure out how
to insert a few lines of text as a footer to all mail passing through an
exim installation.  I have searched high and low and can't seem to find
a way how to do this.

I have read the Exim FAQ regarding this, and I understand that it will
break PGP/GPG signed mails, however I've been asked to investigate this
as part of a work requirement... so no choice here.

I understand that there is always the problem of MIME parts in mails,
and this is why I thought there may be a convenient way around this (for
example using exiscan's mime unpacking feature).

I did look at MIME alteration packages such as AlterMIME, however as
this particular package and others I looked at don't support appending
text via standard out (which I'd need if I were to use
transport_filter), I can't use those.

If exiscan doesn't support this, I'd appreciate any suggestions to a
utility that does this (preferably written in C as I need the speed).

Cheers,
Mike.