what is "unable to fork" email err message means?

[M K Saravanan <mksarav@xxxxxxxxxxxxxxxxx>]

hi,

when one of my friend tried to send a mail to some yahoo ids., he got the
following returned mail from mailer-daemon.  I am not able to understand these
error messages.  Any Clue?

-- mks --


=========================================
Date: 3 Apr 2001 15:30:34 -0000
From: MAILER-DAEMON@xxxxxxxxx
To: prasannadavid@xxxxxxxxx
Subject: failure delivery

Message from  yahoo.com.
Unable to deliver message to the following address(es).

<snrsk@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<k_mohans@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<bkumarashanmugam@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<kars_77@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<ramesh_sur@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<rudhbaskaran@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<s.poongothai@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<ssundar04@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

<visna_s@xxxxxxxxx>:
Unable to fork: temporary failure. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

--- Original message follows.

Return-Path: <prasannadavid@xxxxxxxxx>
X-Track: 1: 40
Received: from 203.197.142.200  (EHLO aukbc3.aukbc.org) (203.197.142.200)
  by mta439.mail.yahoo.com with SMTP; 02 Apr 2001 07:20:30 -0700 (PDT)
Received: from yahoo.com ([192.168.2.32])
	by aukbc3.aukbc.org (8.9.3/8.9.3) with ESMTP id TAA13446;
	Mon, 2 Apr 2001 19:55:59 +0530
Message-ID: <3AC88ACA.FD351FEB@xxxxxxxxx>
Date: Mon, 02 Apr 2001 19:50:58 +0530
From: G Prasanna David <prasannadavid@xxxxxxxxx>
Organization: AU-KBC Centre for Internet & Telecom Technologies
X-Mailer: Mozilla 4.74 [en] (WinNT; U)
X-Accept-Language: en
MIME-Version: 1.0
To: visna_s@xxxxxxxxx, ramesh_sur@xxxxxxxxx, bkumarashanmugam@xxxxxxxxx,
        rudhbaskaran@xxxxxxxxx, snrsk@xxxxxxxxx, kars_77@xxxxxxxxx,
        k_mohans@xxxxxxxxx, ssundar04@xxxxxxxxx, mksarav@xxxxxxxxxxxx,
        s.poongothai@xxxxxxxxx
Subject: [Fwd: [mccmca97] Good One]
Content-Type: multipart/alternative;
 boundary="------------47D2DA03AA03EF53E278930D"


--------------47D2DA03AA03EF53E278930D
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit



> 2000 B.C. - Here, eat this root.
> 1000 A.D. - That root is heathen. Here, say this prayer.
> 1850 A.D. - That prayer is superstition. Here, drink this potion.
> 1940 A.D. - That potion is snake oil. Here, swallow this pill.
> 1985 A.D. - That pill is ineffective. Here, take this antibiotic.
> 2000 A.D. - That antibiotic is artificial. Here, eat this root