PKI Tutorials - Herong's Tutorial Examples - v2.20, by Dr. Herong Yang
Valid Certificate Required in Outlook
This section describes how to request digital signature and encryption when sending an outgoing email message in MS Office Outlook 2007. An invalid certificate error message shows up if you don't have any personal certificate that matches your email address and is issued from a trusted root CA.
Now let's try to send a test email message with encryption and digital signature.
1. Run Outlook and click "New" to create a new test email message.
2a. In Output 2013, Click the "Options > Permissions > Confidential View Only",
2b. In Output 2007, Click the Digital Signature icon and the Encrypt icon in the "Options" menu group under the "Message" menu.
3. Click the "Send" button. Outlook displays an error message: "Microsoft Office Outlook cannot sign or encrypt this message because your certificate is not valid." See the picture below:
Looks like I need good certificate that matches my email address and signed by a trusted root CA to be able to use Outlook S/MIME encryption and digital signature functions.
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