[exim] Redirecting large incoming emails

Hi - A client of mine wants all incoming emails greater than a certain size to be 'redirected' to a 'super user'

I tried to solve it using a filter, but it seems filters only work on a per-user basis (?)

/etc/exim/myfilter:

# Exim filter
if $message_size is above 8m
then
deliver attachments@???
seen finish
endif


And I added this router in my exim.conf:
ourfilter:
driver = redirect
domains = +local_domains
check_local_user
no_check_owner
file = /etc/exim/myfilter

I get the following:

2009-08-19 21:07:36 unable to set gid=1016 or uid=1016 (euid=93): ourfilter router (recipient is annw@???)
2009-08-19 21:07:37 internal problem in ourfilter router (recipient is annw@???): failure to transfer data from subprocess: status=0100 readerror='Success'

Can anybody out there help, please?!

thanks
regards,
Keith