Q198415: XFOR: Disable 8-BIT MIME Support on NT Option Pack SMTP Service

Article: Q198415
Product(s): Microsoft Exchange
Version(s): winnt:4.0,5.0,5.5
Operating System(s): 
Keyword(s): exc4 exc5 exc55
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft Exchange Server, versions 4.0, 5.0, 5.5 
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SUMMARY
=======

Exchange Server administrators may notice the following error message:

  500 Host does not support 8bitmime

This may be a result of a mail host attempting to send 8-bit MIME messages to the
Exchange Server computer. The Microsoft Windows NT Option Pack comes with an
SMTP service that can be used as a relay host between the Internet and Exchange
Server. By default, this SMTP service advertises and allows 8- bit MIME messages
to be relayed. This article describes how to prevent outside mail hosts from
sending in 8-bit MIME messages by disabling the advertisement of 8BITMIME.

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

To make the Windows NT 4.0 SMTP service stop advertising 8BITMIME, you need to
alter the metabase key that tells it to advertise 8BITMIME. Use the Mdutil.exe
utility that is included on the Windows NT Option Pack CD.

NOTE: The Mdutil.exe utility is not installed with the Option Pack by default.

To turn the 8BITMIME advertising off, set the advertisement of 8BITMIME to 0 by
typing the following command at a command prompt:

  mdutil.exe set -path:smtpsvc -prop:36865 -utype:UT_SERVER -dtype:DWORD -
  attrib:INHERIT -value:0

NOTE: The above command is shown on two lines for convenience, but it should be
typed as one continuous command. You may need to stop and restart the SMTPSVC
for this option to take effect. To verify that disabling or enabling 8BITMIME
has taken effect, do the following:

1. From a command prompt, type the following command:

  telnet localhost 25

  After it connects, you should see a banner response with "ESMTP spoken here."

2. On the Terminal menu, click Preferences, verify that the Local Echo check box
  is selected, and then click OK.

3. In the Telnet window type the following command:

  EHLO <yourdomain.com>

  Where <yourdomain.com> is your e-mail domain, and then press the ENTER
  key. You should then receive a response of 250- and various options. If you
  disabled the 8BITMIME, it should no longer be listed.

4. Type "quit" (without the quotation marks) in the Telnet window to close the
  session, and then close the Telnet window.

The response should be:

  36865                         : [IS]    (DWORD)  0x0={0}

The number at the beginning of the returned line, 36865, is the property ID
number for 8BITMIME. The hexadecimal value (0x0)={0} means that 8BITMIME
advertising is turned off.

To turn MIME broadcasting back on, execute the above command after replacing
"-value:0" (without the quotation marks) with "-value:1" (without the quotation
marks). This sets the parameter value to 1, which turns MIME broadcasting on.

Additional query words: 8bit 7bit eight bit

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Keywords          : exc4 exc5 exc55 
Technology        : kbExchangeSearch kbExchange500 kbExchange550 kbExchange400 kbZNotKeyword2
Version           : winnt:4.0,5.0,5.5
Issue type        : kbhowto

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