Import and use digital IDs with Microsoft Outlook Web App (OWA)
To use a digital ID with Outlook Web App (OWA) you need a special component for your WWW browser, an “S/MIME control”. Such a control exists for Microsoft Windows.
If you are able to install this S/MIME control, you are also able to install a “full-fledged” email program.
So it does not make sense to use your digital Id with Outlook Web App. Better use Outlook or another email program.