ICASA email not working

I sent a written complaint by email ********** to ICASA, as per the instruction on the ICASA web site. The complaint about Web9 sending SPAM emails. The email was bounced back with the following error message: "host za-smtp-inbound-2.mimecast.co.za [41.74.193.210] SMTP error from remote mail server after end of data: 554 Email rejected due to security policies" .