When you send a signed email message in a Microsoft Exchange Server 2010 environment, you cannot view the message delivery report by using Microsoft Office Outlook or Microsoft Outlook Web App (OWA). Additionally, you receive the following error message on the Delivery Reports page:
Delivery Reports don’t support tracking messages of this type.
This issue occurs because the delivery report does not support the IPM.Note.SMIME.MultipartSigned message class.
To resolve this issue, install the following update rollup:
2645995 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 2
For more information about the MessageClass element, visit the following Microsoft website: