In a Microsoft Exchange Server 2003 environment, when a user uses Microsoft Outlook Mobile Access to view an e-mail message that was sent from a Microsoft Outlook Web Access client, a message that is similar to the following appears at the top of the e-mail message:
Warning. The signature of this message has not been validated.
The warning does not explain that the message is encrypted and cannot be viewed in Outlook Mobile Access. Therefore, the user cannot see the body of the message, and the user does not know that the body of the message is missing.