Warning: could not send message for past 4 hours

[Mail Delivery Subsystem <MAILER-DAEMON () noname my.domain>]

    **********************************************
    **      THIS IS A WARNING MESSAGE ONLY      **
    **  YOU DO NOT NEED TO RESEND YOUR MESSAGE  **
    **********************************************

The original message was received at Sun, 25 Apr 2004 10:26:02 +0530 (IST)
from [210.212.90.234]

   ----- The following addresses had transient non-fatal errors -----
<vet () alembic co in>

   ----- Transcript of session follows -----
451 4.6.0 Antivirus system malfunction
<vet () alembic co in>... Deferred
Warning: message still undelivered after 4 hours
Will keep trying until message is 1 day old

Reporting-MTA: dns; noname.my.domain
Arrival-Date: Sun, 25 Apr 2004 10:26:02 +0530 (IST)

Final-Recipient: RFC822; vet@alembic.co.in
Action: delayed
Status: 4.6.0
Last-Attempt-Date: Mon, 26 Apr 2004 01:36:03 +0530 (IST)
Will-Retry-Until: Mon, 26 Apr 2004 10:26:02 +0530 (IST)

Return-Path: <tcpdump-workers () tcpdump org>
Received: from alembic.co.in ([210.212.90.234])
        by noname.my.domain (8.11.7/8.11.4) with ESMTP id i3P4uM526426
        for <vet () alembic co in>; Sun, 25 Apr 2004 10:26:02 +0530 (IST)
Message-Id: <200404250456.i3P4uM526426 () noname my.domain>
From: tcpdump-workers () tcpdump org
To: vet () alembic co in
Subject: Mail Delivery (failure vet () alembic co in)
Date: Sun, 25 Apr 2004 10:37:17 +0530
MIME-Version: 1.0
Content-Type: multipart/related;
        type="multipart/alternative";
        boundary="----=_NextPart_000_001B_01C0CA80.6B015D10"
X-Priority: 3
X-MSMail-Priority: Normal