NDR 5.7.1 in SMTP Conn Exchange 2000 with AD Windows 2003   

Hello to all, I have a problem in the following environment:
- 1 Forest with Windows Server 2003 Active Directory and 1 Domain.
- 1 Site in the main building with 2 domain controllers Windows Server 2003 
SP1 (DC1 and DC2).
  In this site I have 2 additional servers of Exchange 2000 SP3 on Windows 
2000 SP4 (member servers: ExchSrv1 and ExchSrv2).
  "ExchSrv1" is the back-end for mailboxes and public folders and "ExchSrv2" 
is dedicated to X.400 Connectors and the SMTP Connector that is used for the 
Internet.
- 6 Sites in the branches with 1 domain controller Windows 2000 Server SP4 
(DC3, DC4, DC5, DC6, DC7 and DC8).
  In five of those sites is the back-end servers of each branch with 
Exchange 2000 Server SP3 on Windows 2000 Server SP4 (domain controllers).

All the domain controllers Windows 2000 and Windows 2003 of the Windows 2003 
forest are Global Catalog Servers.
The execution of the DCDIAG /e in all DCs shows all the tests passed 
sucessfully and in fact the AD replication is working without problems.
The servers are with the last services packs and security patches at level 
of Windows 2000, Windows 2003 and Exchange 2000.
All the Exchange 2000 have applied the August 2004 Exchange 2000 Server 
Post-Service Pack 3 Update Rollup (870540).

Problem: On the Exchange server "ExchSrv2" of the main building they 
constantly change the permissions at level of "delivery restrictions" of the 
SMTP Connector to the Internet (mailboxes are added or retired). Any 
authorized mailbox today cannot send mail but after almost one week, until 
while when sending messages to external SMTP addresses the following NDR is 
generated:

Delivery Notification Status (Failure)
       The following recipient(s) could not be reached: 
       user@hotmail.com on 08/17/2005 11:00
       You do not have permission to send to this recipient.  For
       assistance, contact your system administrator.
       <mail.domain.com #5.7.1>
(the original data were replaced to protect the identity of my client).

Without doing nothing the users can begin to send messages after that lapse.

Somebody has had this behavior in production? What I make to accelerate this 
in an environment Exchange 2000 with Active Directory of Windows 2003?

Thanks in advance by the commentaries and recommendations.

-- 
Best regards,
Spencer Velastegui,
MCT, MCSE+I on Windows NT 4.0,
MCSE: Messaging on Windows 2000,
MCSA: Messaging on Windows 2003.
http://www.spencer-consulting.net
Guayaquil - Ecuador.

date: Tue, 23 Aug 2005 10:13:01 -0700   author:   Spencer Velastegui