I currently have MS Exchange 2000 installed and access internet mail via a
cable modem using earthlink.net.  Users access their mail via Outlook 2000.

Users can send and receive mail fine except to a few select mail servers
(e.g.  aol.com).  When trying to send mail to these servers a message from
the system administrator is sent:

   The following recipient(s) could not be reached:

   'username@aol.com' on 8/29/2003 7:02 PM

   There was a SMTP communication problem with the recipient's email
server. Please contact your system administrator.

   <servername.domain.local #5.5.0 smtp;550 REQUESTED ACTION NOT TAKEN: DNS
FAILURE>

Is there a configuration setting on either the exchange server or in outlook
that will rectify this problem.

Thanks for your help.

Peter