Infobar message when trying to open an S/MIME message in OWA. This guide explains how you can manually install or deploy the Microsoft S/MIME Control for Outlook on the web. However, adding the required extension isn’t (currently) possible via the traditional means of using the Chrome Web Store or the Microsoft Edge Addons page. S/MIME support for Outlook on the Web (OWA) used to be only available in Internet Explorer but it is now also possible to add this to Google Chrome and the new Microsoft Edge browser.