Tons of messages like this

[alexandru.voicu]

Hi all.
After i installed the new Zimbra Community Edition, 8.0 GA 5434, for two times (at a month interval) i was flooded with tons of messages like this:

Received: from ns.alexvoicu.eu (89.33.12.206) by FMWDMAIL.NTDFMWD.local (10.0.0.16) with Microsoft SMTP Server id 14.1.379.0;
Sun, 7 Oct 2012 18:01:06 -0700
Received: from localhost (localhost [127.0.0.1]) by ns.alexvoicu.eu (Postfix) with ESMTP id 6CFAFBA8C7B
for <n.jazmadarian@fmwd.com>;
Sat, 6 Oct 2012 21:40:31 +0300 (EEST)
X-Virus-Scanned: amavisd-new at alexvoicu.eu
Received: from ns.alexvoicu.eu ([127.0.0.1]) by localhost (ns.alexvoicu.eu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id MoqOFMdGwcUJ for <n.jazmadarian@fmwd.com>;
Sat, 6 Oct 2012 21:40:25 +0300 (EEST) Received: from mixnetworking.ro (unknown [50.28.52.218])
by ns.alexvoicu.eu
(Postfix) with ESMTPSA id BF26BBA5C45
for <n.jazmadarian@fmwd.com>;
Sat, 6 Oct 2012 21:40:24 +0300 (EEST)
Date: Sat, 6 Oct 2012 15:40:23 +0000
From: The Boutin <alexandru.voicu@mixnetworking.ro>
Organization: gwvkffr
X-Priority: 3 (Normal)
Message-ID: <6857269175.20121006154023@mixnetworking.ro>
To: <n.jazmadarian@fmwd.com>
Subject: V.-.I.-.A.-.G.-.R.-.A
MIME-Version: 1.0 Content-Type: text/html;
charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-Path: alexandru.voicu@mixnetworking.ro

It looks like spammers tried to use my server to send unauthorized mails using smtps (465) port, but because i have authentication activated the messages are put in bounce, defer and deferred folders and the server even don't crash are significantly slow down.
And by the way, isn't open relay server...
And for statistics... max number of messages was 1669731

Can anyone have an ideea about this problem???

Thanks for your support.

[vadonka]

activate the cbpolicy server and use the graylisting module, or sipmly install postgrey and use with zimbra.
tutorial found here: Improving Anti-spam system - Zimbra :: Wiki