# configuration associates an action to run to a return value name.
#
# The action can be either a postfix access(5) value or a filter name. Postfix access
-# parameters must be prefixed by 'postfix:'.
+# parameters must be prefixed by 'postfix:'. The text argument given to a postfix reply
+# may contain format strings to be replaced by the parameters of the query. This arguments
+# have the following format: ${fieldname}
#
# eg:
# on_match = postfix:REJECT Blacklisted;
+# on_fail = postfix:450 Greylisted, see http://www.example.org/${sender_domain}.html
#
# Filter:
# Current defined filter types are: