Don't increment bounce score when spam is bounced

My mailhost is bouncing spam mail and my bounce score is incremented, eventually leading to my subscription being disabled.

Don't increment the bounce score when spam/malicious mail is bounced.

Possible solution: do a text analysis before incrementing the bounce score. The bounce mail says "This message was blocked because its content presents a potential 552-5.7.0 security issue." Don't increment the bounce score when this message is present.

	This is a Mailman mailing list bounce action notice:

	   List:       Bestuur
	   Member:     edwin@bitstorm.org
	   Action:     Subscription bounce score incremented.
	   Reason:     Excessive or fatal bounces.



	The triggering bounce notice is attached below.

	Questions? Contact the Mailman site administrator at
	mailman@lists.fronteers.nl.

	Van: MAILER-DAEMON@mailmanlists.eu (Mail Delivery System)
	Onderwerp: Undelivered Mail Returned to Sender
	Datum: 28 augustus 2019 om 09:56:50 CEST
	Aan: bestuur-bounces@lists.fronteers.nl


	This is the mail system at host lux.mailmanlists.eu.

	I'm sorry to have to inform you that your message could not
	be delivered to one or more recipients. It's attached below.

	For further assistance, please send mail to postmaster.

	If you do so, please include this problem report. You can
	delete your own text from the attached returned message.

	                  The mail system

	<edwin@bitstorm.org>: host aspmx.l.google.com[64.233.167.27] said: 552-5.7.0
	   This message was blocked because its content presents a potential 552-5.7.0
	   security issue. Please visit 552-5.7.0
	   https://support.google.com/mail/?p=BlockedMessage to review our 552 5.7.0
	   message content and attachment content guidelines. r13si200593wrg.406 -
	   gsmtp (in reply to end of DATA command)
	Reporting-MTA: dns; lux.mailmanlists.eu
	X-Postfix-Queue-ID: 215E72EDA5
	X-Postfix-Sender: rfc822; bestuur-bounces@lists.fronteers.nl
	Arrival-Date: Wed, 28 Aug 2019 09:56:49 +0200 (CEST)