Encrypt messages by using S/MIME in Outlook on the web
The first step to use S/MIME is to obtain a certificate from your IT administrator or helpdesk. Your certificate might be stored on a smart card, or might be a file that you store on your computer. Follow the instructions provided by your organization to use your certificate. Install the S/MIME control.
Applies To:
Outlook.com, Outlook on the web for Exchange Server 2016, Outlook on the web for Exchange Server 2019