S/MIME settings for Outlook on the web in Exchange Server

As an Exchange administrator, you can set up Outlook on the web (formerly known as Outlook Web App) to allow sending and receiving S/MIME-protected messages. Use the Get-SmimeConfig and Set-SmimeConfig cmdlets to view and manage this feature in the Exchange Management Shell. To open the Exchange Management Shell, see Open the Exchange Management Shell.

For detailed syntax and parameter information, see Get-SmimeConfig and Set-SmimeConfig.

S/MIME in Outlook on the web in Exchange 2019 is supported in Internet Explorer, Edge, Edge with Chromium, and Google Chrome.

Considerations for Chrome

To use S/MIME in Outlook on the web in the Google Chrome web browser, you (or another administrator) must set and configure the Chromium policy named ExtensionInstallForcelist to install the Microsoft S/MIME extension in Chrome. The policy value is maafgiompdekodanheihhgilkjchcakm;https://outlook.office.com/owa/SmimeCrxUpdate.ashx. And note that applying this policy requires domain-joined computers, so using S/MIME in Chrome effectively requires domain-joined computers.

For details about the ExtensionInstallForcelist policy, see ExtensionInstallForcelist.

This step is a prerequisite for using Chrome; it does not replace the S/MIME control that's installed by users. Users are prompted to download and install the S/MIME control in Outlook on the web during their first use of S/MIME. Or, users can proactively go to S/MIME in their Outlook on the web settings to get the download link for the control.