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Q241157: XCON: Send and Receive Mail Through a Demand Dial Router

Article: Q241157
Product(s): Microsoft Exchange
Version(s): winnt:5.5
Operating System(s): 
Keyword(s): exc55
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SUMMARY
=======

You may run into an issue when your connection to the Internet is through a
demand dial router and you are using the Microsoft Exchange Server's Internet
Mail Service. The Internet Mail Service forwards a message just as if it were a
permanent connection. When the router detects that data needs to be sent, it
initiates the dial, and sends the message. Exchange Server cannot tell the
difference between this type of connection and a permanent connection, such as a
T1 or Frame Relay. Most likely, when using a demand dial router, the primary MX
record is your Internet server provider's (ISP's) mail server. The ISP queues
the mail for the final destination. Normally, Exchange Server issues the ETRN
command to the ISP's mail server to de-queue the mail. However, there is no way,
within the Exchange Server Administrator program, to enable ETRN functionality
outside of the normal Internet Mail Service dial-up configuration.

MORE INFORMATION
================

You can tell Exchange Server to always issue the ETRN command to the host
specified in the "Forward all mail to host" field by setting the following
registry parameter.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

1. Start Registry Editor (Regedt32.exe).

2. Locate the following key in the registry:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\
  Parameters

3. On the Edit menu, click Add Value, and then add the following registry value:

  Value Name: AlwaysUseETRN
  Data Type: REG_DWORD
  Value: 0x1

4. Quit Registry Editor.

Now, every time the Internet Mail Service forwards mail to the specified host, it
will also issue the ETRN command to that host. There is no way to issue the ETRN
command to another host. So, for this to work properly, the host that is queuing
the mail also has to be able to relay mail.

One possible drawback to this approach is that incoming mail is only received
when outgoing mail is sent. If this delay is an issue, you can configure an
Exchange Server link monitor to the Internet. The link monitor uses an SMTP
custom recipient that is a false user at a valid domain. The monitor sends a
message to this custom recipient at the specified interval. Because this is an
SMTP message, the Internet Mail Service sends it and also de-queues mail at the
same time. Assuming the connection is functional, the message is returned as
non-deliverable, indicating that the link is active. For the link monitor to
stay active, the Administrator program needs to remain open. For additional
information on configuring a link monitor, please see the Microsoft Exchange
Server 5.5 Administrator's Guide.

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

  Q152959 XADM: How to Remove the First Exchange Server in a Site

Additional query words: AlwaysUseEtrn, dequeue adsl dsl cable modem cablemodem

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Keywords          : exc55 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbhowto

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