Microsoft Outlook cannot sign or encyrpt this message becauase you have no certfificates which can be used to send from your e-mail address

Danish: Denne meddelelse kunne ikke signeres eller krypteres, fordi du ikke har et certifikat, som kan bruges til at sende fra din e-mail-adresse

Error message:

(Danish Error message)

FIX:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security]
"SupressNameChecks"=dword:00000001

Source: https://support.microsoft.com/en-us/help/276597/how-to-turn-off-e-mail-matching-for-certificates-in-outlook