How to turn off 8BITMIME in Windows 2000 and in Windows Server 2003 SMTP service

Microsoft Windows 2000 and Microsoft Windows Server 2003 include a Simple Mail Transfer Protocol (SMTP) service. The SMTP service can be used as a relay host. By default, this SMTP service advertises 8-bit Multipurpose Internet Mail Extensions, also known as 8BITMIME, and lets 8-bit MIME messages be relayed. Some products cannot handle 8-bit MIME messages. Products that cannot handle 8-bit MIME messages include the following:

• Microsoft Exchange Server version 4.0
• Microsoft Exchange Server version 5.0
• Microsoft Exchange Server version 5.5

This article describes how to turn off the SMTP service so that it does not advertise 8BITMIME. You want to do this to prevent outside mail hosts from sending in 8-bit MIME messages.

Turn off the SMTP verb so that 8BITMIME is not advertised

To do this, you must change the metabase key that lets the SMTP service advertise 8BITMIME. Use the Mdutil.exe file utility that is included on the Windows 2000 CD ROM.

Note By default, the Mdutil.exe file utility is not installed with Windows 2000. The Mdutil.exe file utility is located in the \i386 directory and is named Mdutil.ex_.

1. Copy the Mdutil.exe file utility to your local disk.
2. Run the following command to extract the utility:
   
   Expand Mdutil.ex_ Mdutil.exe
3. Turn off 8BITMIME. To do this, you must modify a metabase key on the SMTP Server Instance level.
4. Determine how many SMTP Virtual Server instances are configured. You can do this by using the following command:
   
   Mdutil.exe enum -path:smtpsvc
   
   You are supposed to see entries, such as the following:
   • [/smtpsvc/1]
   • [/smtpsvc/2]
   • [/smtpsvc/3]
   Each entry represents an SMTP Virtual Server instance. You must look in the Microsoft Management Console (MMC) to find the SMTP Virtual Server instance that you want to modify. The SMTP Virtual Server instances are listed from top to bottom.

Obtain the original property value

To turn off 8-bit MIME support for this specific instance, you must change one bit in the metabase property 36998. You first must obtain the original value of this property, switch off this bit, and then write the new value back to the metabase. To do this, follow these steps:

1. To obtain the original property value, follow these steps:
   1. Type the following command at the command prompt:
      
      Mdutil.exe get -path:smtpsvc/<n> -prop:36998
   2. Replace <n> with the number of the SMTP Virtual Server instance that you want to modify.
      
      If you receive the following error message, the metabase property 36998 is not stored in the properties of this SMTP Virtual Server instance:
      Error: GetData - HRES(0x800cc801) MD_ERROR_DATA_NOT_FOUND
   3. If you receive the previous error message, use the following command to retrieve the value from the SMTP master properties. You can use the following command because this value is inherited by all instances that do not have the property set explicitly.
      
      Mdutil.exe get -path:smtpsvc -prop:36998
      
      The response is supposed to be similar to the following:
      
      36998 : [IS] (DWORD) 0x7574c1={7697601}
2. Turn off the bit that is responsible for 8BITMIME support.
   
   The responsible bit is represented by the following mask:
   
   0x0400000.
   
   To turn off this bit, you must do a bitwise AND operation on the property value that has 0xFBFFFFF.
   
   To do this, follow these steps:
   1. Start Calculator. Switch Calculator to Scientific view
   2. Switch Calculator to Hex-Mode.
   3. Enter the hexadecimal property value.
      
      In this example, the property value is 7574c1.
   4. Click AND, and then type FBFFFFF.
      
      The result is the new property value that you must set in the metabase. In this example, the new property value is 3574c1.
3. Write the new value back to the metabase.
   
   All changes to this metabase property are supposed to be made on the instance level. If you took the property from the master properties, write the property back to the specific SMTP Virtual Server instance.
4. Replace the property value for the first SMTP Virtual Server instance. To do this, use the following command:
   
   Mdutil.exe set -path:smtpsvc/1 -prop:36998 -utype:UT_SERVER -dtype:DWORD -attrib:INHERIT -value:0x3574c1
   
   Important Replace the property value that is 3574c1 in the upper line with your property value.
   
   The response is similar to the following:
   
   36998 : [IS] (DWORD) 0x3574c1={3503297}
5. Turn on 8-bit MIME. To do this, repeat the previous steps. However, use "OR 0x0400000" instead of "AND 0xFBFFFFF."

For more information about a solution for Microsoft Windows NT Option Pack on NT Server 4.0, click the following article number to view the article in the Microsoft Knowledge Base: For more information about how to create a metabase backup, click the following article number to view the article in the Microsoft Knowledge Base: For more information about how to disable Extended Simple Mail Transport verbs, including 8bitmime, in Microsoft Exchange 2000 Server and Microsoft Exchange Server 2003, click the following article number to view the article in the Microsoft Knowledge Base: