Problème réception smtp (Spam, Virus)

Bonjour à tous,

Je dois avouer que j'ai besoin d'un avis professionnel, je reçois un très grand nombre de message du style :

MailEnable: Message could not be delivered to some recipients.
The following recipient(s) could not be reached:

                Recipient: [SMTP:278998909@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:1154778042@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:851892760@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:783949665@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:65985948@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:1172990053@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:771792587@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:2643894408@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:992986195@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied

                Recipient: [SMTP:2463956892@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox not found. https://service.mail.qq.com/cgi-bin/help?subtype=1&&id=20022&&no=1000728

                Recipient: [SMTP:396962975@qq.com]
                Reason: Remote SMTP Server Returned: 550 Mailbox unavailable or access denied



Message headers follow:

Received: from owxhh ([222.218.152.89]) by masociete with MailEnable ESMTP; Mon, 18 Jun 2012 08:40:54 +0200
Message-ID: <FD1CCB86C1F6DB95100C2280BD5787E5@owxhh>
From: "" <info@masociete.com>
To: <278998909@qq.com>
Subject: =?utf-8?B?ICAgICAgIEhp77ya5p+l55yLICEgICA=?=
Date: Mon, 18 Jun 2012 14:39:31 +0800
MIME-Version: 1.0
Content-Type: multipart/alternative;
                boundary="----=_NextPart_000_0461_01AED699.10FAB180"
X-Priority: 1
X-MSMail-Priority: High
X-Mailer: Microsoft Outlook Express 6.00.2900.5512
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5512

Avez-vous un avis sur la chose, spam ? Virus ? Ordinateur fatigué ?
Merci d'avance pour votre aide