[Exim] Help ! problem with ACLs

Hi,

I have recently installed exim 4.30 + exiscan onto our departmental
mailserver. I have got it virus scanning emails
as they come in and go out, however this server is also a relay for our
lgacy novell/mercury mail system. Users on the
legacy ssytem often have forwards set up to redirect their mail
elsewhere. When this happens however the mail is
scanned by spamassassin twice leading to a second set of X-Spam headers
bein appended.

What I would idealy like to do is to be able to check for the existance
of the headers and not re-insert them if they exist.

I am tying to use a condition ( def:header_ ) to the warn statement that
inserts the header flag, however which ever way
I write it I seem to either never get headers or get errors reported in
the mainlog, and no delivery done.

I am trying to use something like this :-

        warn    message         = X-Spam-Score: $spam_score
                    spam             = nobody:true
                    condition       = "${if
def:header_x-spam-score:{$h_x-spam-score:}{$h_from:}}"

If anyone can help I'd be most greatfull !

Thanks,

Phill.