[Exim] System Filters failing.

HI,

I'm having some trouble with filtering messages. I copied and installed the
sample Windows Executable Content filter from the exim.org site. The
problem is it won't block messages with the listed attachments.

Reading through the mailing list I have added the following to my exim.conf

message_filter_user = blah
message_filter_group = blah
message_filter = /etc/exim/system_filter.exim
message_body_visible = 10000
message_filter_directory_transport = address_directory
message_filter_file_transport = address_file
message_filter_pipe_transport = address_pipe
message_filter_reply_transport = address_reply

I'm running Exim 3.22 on the Debian distribution.

Regards,
Ed.