PostFix: Refuse 'spam' mail ?

[Michael Kaaber <kaaber@fak.hum.ku.dk>]

I run OpenBSD 2.8 and PostFix Snapshot-20001005

In the main.cf I have setup:

  maps_rbl_domains = rbl.maps.vix.com, dul.maps.vix.com

I receive spam from 'hahaha@sexyfun.net' with a virus 'W32/Hybris-B' in the
Attachment.

How did I setup PostFix refuse mail from 'sexyfun.net' ?

I is possible to send a 'refuse' mail back to the user ?

Here is the header:

 Return-Path: <>
 Delivered-To: kaaber@r23.dk
 Received: from e7d8c1 (p85.as2.kanturk1.eircom.net [159.134.208.85]) 
	by r23.dk (Postfix) with SMTP id 869F34A45
	for <kaaber@r23.dk>; Thu, 31 May 2001 00:02:37 +0200 (MEST)
 From: Hahaha <hahaha@sexyfun.net>
 Subject: Snowhite and the Seven Dwarfs - The REAL story!
 MIME-Version: 1.0
 Content-Type: multipart/mixed; boundary="--VE6ZS92JK52BW9YB8LAZ05URSDINW9"
 Message-Id: <20010530220237.869F34A45@r23.dk>
 Date: Thu, 31 May 2001 00:02:37 +0200 (MEST)
 To: undisclosed-recipients:;
 X-IMAPbase: 991397519 4
 Status: RO
 X-Status: 
 X-Keywords:                       
 X-UID: 1

Regards
 Michael.