Exim filter not working with email forward

I have server mail with forward to a yahoo email, but I wan't send email forward if email have header from domain is "@yahoo.com".

Begin i try will block all email forwarder to email "someusr@yahoo.com" but it filter not working, Emails still forwarder to email "someusr@yahoo.com",

My Filter:

Code:

if $header_to: contains "someusr@yahoo.com"
then
fail text "Your message to inform email users about the problem..."
finish
endif
if not first_delivery
then
finish
endif

Please help me ! Thanks