Q274241: XADM: Digitally Signed Messages Received Without Signature

Article: Q274241
Product(s): Microsoft Exchange
Version(s): 5.5 SP3
Operating System(s): 
Keyword(s): exc55sp3
Last Modified: 23-OCT-2000

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 SP3 
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SYMPTOMS
========

When you send a message that has a digital signature, the message may be
received without the signature.

CAUSE
=====

In Exchange Server 5.5, the Internet Mail Service does not deliver signed
messages by default. Messages that are sent with a digital signature are
modified by the Internet Mail Service and delivered without the signature.

RESOLUTION
==========

To resolve this issue, change the Internet Mail Service to allow S/MIME
signatures:

1. Start the Exchange Server Administrator program, and go to the Connectors
  container.

2. Double-click Internet Mail Service.

3. Click the Internet Mail tab.

4. Click to select the "Clients support S/MIME signatures" check box.

5. Restart the Internet Mail Service.

CLIENT-SIDE WORKAROUND

If you are sending messages from a client computer, you can encode the signature
and message to prevent the signature from being removed:

1. Start Outlook Express, and on the Tools menu, click Options.

2. Click the Security tab and click the Advanced button.

3. Click to select the "Encode message before signing (opaque signing)" check
  box.

When you use this option to encode the message, the process is similar to
encrypting the message. However, this option does not require the receiver to
have a certificate to decode the message. An S/MIME-aware client can decode and
view the message. Non-S/MIME-aware clients receive the message in an attached
file, Smime.p7m.

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

The mail icon for a message that is sent with a digital signature is marked with
a red ribbon. If you save a copy of the message in the Sent Items folder, you
can check if the message that was sent has a digital signature by checking to
see whether the message is marked with a red ribbon.

The following information about the "Clients support S/MIME signatures" option
can be found in the Exchange Administrator program Online Help:

  Enable if your clients support S/MIME signatures (MIME multipart/singed).
  Disable to convert messages with S/MIME signatures (MIME signed messages) to
  MIME unsigned messages. This allows recipients using e-mail client programs
  that don't support S/MIME to view signed messages.

Additional query words:

======================================================================
Keywords          : exc55sp3 
Technology        : kbExchangeSearch kbZNotKeyword2 kbExchange550SP3
Version           : :5.5 SP3
Issue type        : kbprb

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