DOCUMENT:Q258745 11-JUN-2002 [exchange] TITLE :XIMS: Internet Mail Service Displays SMTP Banner Slowly PRODUCT :Microsoft Exchange PROD/VER:winnt:5.5 OPER/SYS: KEYWORDS:exc55 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Exchange Server, version 5.5 ------------------------------------------------------------------------------- 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 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: 1. Start Registry Editor (Regedt.exe). 2. Locate the following key in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC\Parameters 3. On the Edit menu, click New DWORD Value. 4. Type "DisableReverseResolve" (without the quotation marks). 5. Under "Value data", type "1" (without the quotation marks). 6. Quit Registry Editor. If you use Regedt32.exe: 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: DisableReverseResolve Data Type: REG_DWORD Radix: Binary Value: 1 4. 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 : exc55 Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 Version : winnt:5.5 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.