Article ID: 258745
Article Last Modified on 10/28/2006
APPLIES TO
- Microsoft Exchange Server 5.5 Standard Edition
This article was previously published under Q258745
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
SYMPTOMS
After you make a connection to an Exchange Server computer Internet Mail Service on port 25, the Simple Mail Transfer Protocol (SMTP) banner may not be displayed quickly, which may cause certain SMTP applications to time out.
CAUSE
This issue can occur because Exchange Server performs a reverse lookup on all connections. A reverse lookup may take several seconds because of a lack of or incorrectly configured Domain Name System (DNS) servers.
RESOLUTION
To resolve this issue, increase Internet Mail Service performance by disabling reverse resolution. To do this, 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.
If you use Regedit.exe:
- Start Registry Editor (Regedt.exe).
- Locate the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC\Parameters
- On the Edit menu, click New DWORD Value.
- Type DisableReverseResolve.
- Under Value data, type 1.
- Quit Registry Editor.
If you use Regedt32.exe:
- Start Registry Editor (Regedt32.exe).
- Locate the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC\Parameters
- On the Edit menu, click Add Value, and then add the following registry value:
Value Name: DisableReverseResolve
Data Type: REG_DWORD
Radix: Binary
Value: 1 - Quit Registry Editor.
MORE INFORMATION
Reverse resolution occurs when the name of the host that delivered an incoming SMTP message is resolved and placed in the message header by the Internet Mail Service. When reverse resolution is disabled, the Internet Mail Service does not resolve the host name in the upper-most Received From field of the SMTP message header. If the address is in Internet Protocol (IP) form, it remains in IP form.
Additional query words: Smart Host, IMS
Keywords: kbprb KB258745
