Restricting rejections

This is a small part of my procmail recipe:

BAN_REGEXP = "estacio\.br"

:0
* $ ()\/$BAN_REGEXP
{
reject=$MATCH

It is rejecting even if the banned domain is included in the To: field.

How can I change this? Just modifying to:

:0
* $ (From|Reply-To|Return-Path|Sender)\/$BAN_REGEXP
{
reject=$MATCH

??? I tried but it did not work...

Thanks!

Hermann