Hi Julius,
I do not use Hotmail, I use the Windows Live Mail app for my 3rd Party email.
I have tried all using webmail and these work fine, I only find some email addresses in my address book within Windows Live Mail give this error message, I have tried deleting etc and it still does not work.
If the people in your contacts/address book use digital IDs you would need to export their certificate and then import it into their contact entry (the ID tab for the contact).
http://windows.microsoft.com/en-us/windows-live/windows-live-essentials-release-notes
S/MIME certificates need to be re-established
S/MIME (Secure/ Multipurpose Internet Mail Extensions) is a security standard for public key encryption and the signing of e‑mail with a digital ID or certificate. If you use the Secure Mail (certificates) feature of
Windows Live Mail to send or receive mail, you'll need to re-establish your S/MIME certificate and the certificates of each of your contacts with whom you exchange secure e‑mail.
You can set up your own S/MIME certificate by selecting the correct certificate in
Windows Live Mail:
- In Windows Live Mail, click the
Menu button on the toolbar, and then click
Safety options.
- Click the Security tab.
- In the Secure Mail section, click
Digital IDs.
- In the Certificates dialog box, select the certificate you use for your S/MIME e‑mail.
You can set up the certificate for each of your contacts by adding the certificate to your contact list:
- In the main window of Windows Live Mail, select an e‑mail message you've received from that contact that includes a digital certificate.
- Click the certificate icon for that e‑mail.
- Click View certificates.
- Click Add to contacts.