[Exim] can't currently verify any sender in the header lines

Why is this mail not being accepted?
In this case, exim complains that the header From's domain doesn't
resolve and maybe (I can't tell for sure from the error message) that
wwwac@??? isn't accepted by focazio.com's MX, but yet both are
false:

2001-02-09 10:05:06 14RHuo-0000Qe-00 rejected from celia.wwwac.org [209.73.238.1
00.14109]: can't currently verify any sender in the header lines (envelope sende
r is <wwwac-return-53544-arijort=valinux.com@???>) - try later
Recipients: arijort@???
P Received: from celia.wwwac.org ([209.73.238.100.14109])
        by mail.valinux.com with smtp (Exim 3.22 #1 (Debian))
        id 14RHuo-0000Qe-00
        for <arijort@???>; Fri, 09 Feb 2001 10:05:02 -0800
P Received: (qmail 3809 invoked by uid 502); 9 Feb 2001 18:05:27 -0000
  Mailing-List: contact wwwac-help@???; run by ezmlm
  Precedence: bulk
  X-No-Archive: yes
  list-help: <mailto:wwwac-help@lists.wwwac.org>
  list-unsubscribe: <mailto:wwwac-unsubscribe@lists.wwwac.org>
  list-post: <mailto:wwwac@lists.wwwac.org>
  Delivered-To: mailing list wwwac@???
  X-Ezauth: anehpidkpjpcgaepbglp
P Received: (qmail 3799 invoked from network); 9 Feb 2001 18:05:25 -0000
  Mime-Version: 1.0
  X-Sender: wwwac@???
I Message-Id: <p05010405b6a9d2e8b52e@???>
  In-Reply-To: <5168130B695FD21194050008C79CF2E57333C7@MAIL>
  References: <5168130B695FD21194050008C79CF2E57333C7@MAIL>
  Date: Fri, 9 Feb 2001 12:11:59 -0500
T To: "Paul R. Dube, Jr." <dube@???>, Wwwac <wwwac@???>
F From: "Martin T. Focazio" <wwwac@???>
  Content-Type: text/plain; charset="us-ascii" ; format="flowed"
  Subject: Re: [wwwac] WHAT'S UP WITH WIRELESS?

kenny:/etc/mail/checksender# nslookup -type=MX focazio.com
Server: localhost.valinux.com
Address: 127.0.0.1

focazio.com     preference = 5, mail exchanger = mail.focazio.com
focazio.com     nameserver = dns1.interland.net
focazio.com     nameserver = dns2.interland.net
focazio.com     nameserver = dns3.interland.net
mail.focazio.com        internet address = 64.224.62.63
dns1.interland.net      internet address = 64.224.20.132
dns2.interland.net      internet address = 64.224.20.133
dns3.interland.net      internet address = 64.224.20.134

kenny:/etc/mail/checksender# telnet mail.focazio.com smtp
Trying 64.224.62.63...
Connected to mail.focazio.com.
Escape character is '^]'.
220 X1 NT-ESMTP Server mail.focazio.com (IMail 6.04 1947729-1)
helo foo
250 hello mail.focazio.com
mail from: postmaster@???
250 ok
rcpt to: wwwac@???
250 ok its for <wwwac@???>
quit
221 Goodbye
Connection closed by foreign host.
-- 
Microsoft is to operating systems & security ....
                                      .... what McDonalds is to gourmet cooking

Home page: http://marc.merlins.org/ | Finger marc_f@??? for PGP key