When a Microsoft Exchange Server 2007-based Edge server receives signed e-mail messages that have an attachment from the Internet, the Microsoft Outlook MAPI users receive the messages. However, the digital signature is invalid. If you click the signature icon in Microsoft Outlook, you receive the following error message:

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This problem occurs because the Attachment Filter agent adds the Content-Description field together with the file name of the attachment to the message. For the messages that are signed, this modification invalidates the digital signature.

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Update information

To resolve this problem, install Update Rollup 2 for Exchange Server 2007 Service Pack 1 (SP1) on the Exchange server. For more information, click the following article number to view the article in the Microsoft Knowledge Base: After you install Update Rollup 2 for Exchange Server 2007 SP1, add the following line in the Edgetransport.exe.config file in the <AppSettings> section:

<add key=”SkipDigitalSignedMessageFromAttachmentFilter" value="true" />

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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For more information about the Attachment Filter agent, visit the following Microsoft Web site: For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

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