[Exim] Filtering by subject

Thanks for your help,

Here is what I did and it worked great:

under virtuals:

localuser_spam:
driver = accept
condition = "${if eq {$h_X-Spam-Flag:}{YES} {1}{0}}"
transport = local_delivery_spam

Under Routers:

local_delivery_spam:
driver = appendfile
file = /var/spool/exim/spam/$local_part
delivery_date_add
envelope_to_add
return_path_add