XFOR: Disabling Outbound ESMTP (194132)


The information in this article applies to:

  • Microsoft Exchange Server 5.5
  • Microsoft Exchange 2000 Server
This article was previously published under Q194132
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:

256986 Description of the Microsoft Windows Registry

SUMMARY

Under specific circumstances, dependent your messaging environment, network, and topology, you may need to disable sending the EHLO command to a remote host from the Exchange Server 5.5 Internet Mail Service or Exchange 2000 Server SMTP connector. If an Exchange Server 5.5 Internet Mail Service or Exchange 2000 SMTP connector connects to another mail host that is functioning properly, the mail host sends back the following banner:

20 host_fully_qualified_domain_name Server SMTP ready at Thu, 27 Aug 1998 10:57:09 +0100

When you send the EHLO command (sent by default in Exchange Server 5.5 and Exchange 2000), to a mail host that either doesn't have support for the command or is disabled, you receive the following message:

ehlo Microsoft.com
550 Unknown command 'ehlo

To disable sending the EHLO command by default and send a standard HELO command instead, perform one of the following procedures, as applicable:
  • In Exchange Server 5.5, you need to edit the registry: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: DisableOutboundESMTP
      Data Type: REG_DWORD
      Value: 1

    4. Quit Registry Editor.
    5. Stop and restart the Internet Mail Service.
  • In Exchange 2000, create an SMTP connector, and then configure the SMTP connector to use HELO instead of EHLO in the advanced options:
    1. Start System Manager; click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
    2. Locate Connectors.
    3. Right-click the SMTP connector, click Properties, and then click the Advanced tab.
    4. To send the HELO start message and use standard SMTP and not extended SMTP, click Send HELO instead of EHLO.
After you perform these steps, when the Exchange Server Internet Mail Service or Exchange 2000 SMTP connector initiates a connection to any other SMTP or ESMTP mail host, the Exchange Server Internet Mail Service or Exchange 2000 SMTP connector only sends the HELO command.
Modification Type:MinorLast Reviewed:4/28/2005
Keywords:kbinfo KB194132
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