[Exim] 550 DNS FAILURE with aol

I get this error when sending to anyone at aol. This is the only smtp I
have problems with. Im on a DSL line (reverse comes back to swbell)

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. The following address(es) failed:

  validusername@???:
    SMTP error from remote mailer after MAIL FROM:<dontspam@???>:
    host mailin-04.mx.aol.com [152.163.224.122]:
    550 REQUESTED ACTION NOT TAKEN:
    DNS FAILURE

------ This is a copy of the message, including all the headers. ------

Return-path: <dontspam@???>
Received: from root by mayor.lansville.com with local (Exim 3.12 #1 (Debian))
         id 15VbyR-00007a-00
         for <validusername@???>; Sat, 11 Aug 2001 11:50:55 -0500
To: validusername@???
Subject: test
Message-Id: <E15VbyR-00007a-00@???>
From: root <dontspam@???>
Date: Sat, 11 Aug 2001 11:50:55 -0500

test