Spam delivered although it should be discarded

[Nikolaos Milas]

Hello,

I am running Postfix with amavisd-new/clamav/spamassassin as an incoming 
mail gateway server.

The basic Amavis settings are:

    $final_virus_destiny = D_DISCARD;
    $final_banned_destiny = D_DISCARD;
    $final_spam_destiny = D_DISCARD;
    $final_bad_header_destiny = D_PASS;

So, I would expect the message with the following headers to be 
discarded, but it was delivered:

X-Virus-Scanned: amavisd-new at noa.gr
X-Spam-Flag: YES
X-Spam-Score: 7.287
X-Spam-Level: *******
X-Spam-Status: Yes, score=7.287 tagged_above=-999 required=6.31
     tests=[AV:Doppelstern.Scam4.4628.UNOFFICIAL=5, DKIM_SIGNED=0.1,
     DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25,
     FREEMAIL_FROM=0.001, FROM_LOCAL_NOVOWEL=0.5, HK_RANDOM_ENVFROM=0.626,
     HK_RANDOM_FROM=0.999, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001,
     T_FREEMAIL_DOC_PDF=0.01] autolearn=no
Authentication-Results: mailgw1.noa.gr (amavisd-new); dkim=pass 
(1024-bit key)
     header.d=att.net; domainkeys=pass (1024-bit key)
     header.from=webxxxxxx123451234 at att.net header.d=att.net
Received: from mailgw1.noa.gr ([127.0.0.1])
     by localhost (mailgw1.noa.gr [127.0.0.1]) (amavisd-new, port 10024)
     with LMTP id F5YaLbWUBBjJ for <mailmanager at astro.noa.gr>;
     Tue, 26 Feb 2013 00:39:32 +0200 (EET)

Can someone please explain why this mail was delivered and how should I 
avoid delivering spam? (Normally, I have it quarantined.)

Thanks in advance,
Nick