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:

Outlook Invalid Certificate Error
Outlook Invalid Certificate Error

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.

Table of Contents

 About This Book

 Introduction of PKI (Public Key Infrastructure)

 Introduction of HTTPS (Hypertext Transfer Protocol Secure)

 Using HTTPS with Google Chrome

 Using HTTPS with Mozilla Firefox

 HTTPS with Microsoft Edge

 Using HTTPS with Apple Safari

 HTTPS with IE (Internet Explorer)

 Android and Server Certificate

 iPhone and Server Certificate

 Windows Certificate Stores and Console

 RDP (Remote Desktop Protocol) and Server Certificate

 macOS Certificate Stores and Keychain Access

 Perl Scripts Communicating with HTTPS Servers

 PHP Scripts Communicating with HTTPS Servers

 Java Programs Communicating with HTTPS Servers

 .NET Programs Communicating with HTTPS Servers

 CAcert.org - Root CA Offering Free Certificates

 PKI CA Administration - Issuing Certificates

 Comodo Free Personal Certificate

 Digital Signature - Microsoft Word

 Digital Signature - OpenOffice.org 3

S/MIME and Email Security

 What Is S/MIME

 Digital Signature Scheme for Email Messages

 A Simple Email Message Example

 Email Messages with Attachments using MIME

 Email Messages with Digital Signatures using S/MIME

 Encrypted Email Messages using S/MIME

 Digital Signature and Encryption in Outlook

 Email Security Settings in Outlook

Valid Certificate Required in Outlook

 Message Security Properties in Outlook 2007

 Firefox Extension - Gmail S/MIME

 PKI (Public Key Infrastructure) Terminology

 Outdated Tutorials

 References

 Full Version in PDF/EPUB