linux问题！！

From MAILER-DAEMON@ibm366-4  Sun Mar 18 08:43:52 2007
Return-Path: <MAILER-DAEMON@ibm366-4>
Received: from localhost (localhost)
        by ibm366-4 (8.13.1/8.13.1) id l2I0hqCI026856;
        Sun, 18 Mar 2007 08:43:52 +0800
Date: Sun, 18 Mar 2007 08:43:52 +0800
From: Mail Delivery Subsystem <MAILER-DAEMON@ibm366-4>
Message-Id: <200703180043.l2I0hqCI026856@ibm366-4>
To: postmaster@ibm366-4
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
        boundary="l2I0hqCI026856.1174178632/ibm366-4"
Subject: Postmaster notify: see transcript for details
Auto-Submitted: auto-generated (postmaster-notification)
Status: O

This is a MIME-encapsulated message

--l2I0hqCI026856.1174178632/ibm366-4

The original message was received at Tue, 13 Mar 2007 08:43:52 +0800
from localhost
with id l2D0hquo032705

   ----- The following addresses had permanent fatal errors -----
<root@ibm366-4>

   ----- Transcript of session follows -----
451 ibm366-4: Name server timeout
Message could not be delivered for 5 days
Message will be deleted from queue

--l2I0hqCI026856.1174178632/ibm366-4
Content-Type: message/delivery-status

Reporting-MTA: dns; ibm366-4
Arrival-Date: Tue, 13 Mar 2007 08:43:52 +0800

Final-Recipient: RFC822; root@ibm366-4
Action: failed
Status: 4.4.7
Last-Attempt-Date: Sun, 18 Mar 2007 08:43:52 +0800

--l2I0hqCI026856.1174178632/ibm366-4
Content-Type: message/rfc822

Return-Path: <MAILER-DAEMON>
Received: from localhost (localhost)
        by ibm366-4 (8.13.1/8.13.1) id l2D0hquo032705;
        Tue, 13 Mar 2007 08:43:52 +0800
Date: Tue, 13 Mar 2007 08:43:52 +0800
From: Mail Delivery Subsystem <MAILER-DAEMON>
Message-Id: <200703130043.l2D0hquo032705@ibm366-4>
To: <root@ibm366-4>
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
        boundary="l2D0hquo032705.1173746632/ibm366-4"
Subject: Warning: could not send message for past 4 hours
Auto-Submitted: auto-generated (warning-timeout)

This is a MIME-encapsulated message

--l2D0hquo032705.1173746632/ibm366-4

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

The original message was received at Tue, 13 Mar 2007 04:03:08 +0800
from localhost [127.0.0.1]

   ----- Transcript of session follows -----
451 ibm366-4: Name server timeout
451 ibm366-4: Name server timeout
451 ibm366-4: Name server timeout
Warning: message still undelivered after 4 hours
Will keep trying until message is 5 days old
451 ibm366-4: Name server timeout

--l2D0hquo032705.1173746632/ibm366-4
Content-Type: message/delivery-status

Reporting-MTA: dns; ibm366-4
Arrival-Date: Tue, 13 Mar 2007 04:03:08 +0800

Final-Recipient: RFC822; root@ibm366-4
Action: delayed
Status: 4.4.3
Last-Attempt-Date: Tue, 13 Mar 2007 08:43:52 +0800
Will-Retry-Until: Sun, 18 Mar 2007 04:03:08 +0800

--l2D0hquo032705.1173746632/ibm366-4
Content-Type: message/rfc822

Return-Path: <root@ibm366-4>
Received: from ibm366-4 (localhost [127.0.0.1])
        by ibm366-4 (8.13.1/8.13.1) with ESMTP id l2CK38un024946
        for <root@ibm366-4>; Tue, 13 Mar 2007 04:03:08 +0800
Received: (from root@localhost)
        by ibm366-4 (8.13.1/8.13.1/Submit) id l2CK38Ww024924
        for root; Tue, 13 Mar 2007 04:03:08 +0800
Date: Tue, 13 Mar 2007 04:03:08 +0800
From: root <root@ibm366-4>
Message-Id: <200703122003.l2CK38Ww024924@ibm366-4>
To: root@ibm366-4
Subject: LogWatch for ibm366-4


################### LogWatch 5.2.2 (06/23/04) ####################
       Processing Initiated: Tue Mar 13 04:02:02 2007
       Date Range Processed: yesterday
     Detail Level of Output: 0
          Logfiles for Host: ibm366-4
################################################################



截了一部分，一直在报这样的错，各位看看有什么问题马？？老是看到name server time out。还是只是警告，什么情况下会有类似报错发生呢？？
谢谢！！