Use digital signatures for email with Outlook on the web

On this page:


Before you begin

You can use S/MIME certificates, also called "S/MIME Certs" or "Personal Certificates", with most email clients to digitally sign and/or encrypt email messages. At Indiana University, S/MIME certificates are provided by the InCommon Certificate Service. For instructions on getting a certificate, see Get an S/MIME certificate for digital email signatures at IU.

For details about potential issues with various devices and applications when using digital signatures, be sure to refer to Known issues with digitally signed email at IU.

Note:

This document assumes that you have already published your S/MIME certificate to the Global Address List as described in Use digital signatures for email with Microsoft Outlook for Windows. If not, you will need to follow the instructions for the "Import your certificate" and "Use your certificate with Outlook" sections in Use digital signatures for email with Microsoft Outlook for Windows before you will be able to use the certificate with Outlook on the web.

To view all the content available to you here, use the green Log in button at the top of this page to log into the Knowledge Base.

Overview

To use a digital signature with Outlook on the web, you need to use Microsoft Edge as your browser.

This process is easy to do, but does have to be done in stages that seem to repeat themselves, though they will produce different results at each stage.

Use your digital certificate

Stage 1

  1. Open Edge, and log into Outlook on the web.
  2. Click New message. In the new message window, click the three horizontal dots to the right of "Discard". In that menu, choose Show message options....
  3. In the "Message options" dialog box, check the box for "Digitally sign this message (S/MIME)". Click OK.
  4. Back in the message window, there will be an inline pop-up that says "You can't sign or encrypt this message until the S/MIME extension is installed. To install the extension, click here." Select Click here.
  5. A new tab will open that will take you to the Microsoft Store Add-in for S/MIME. Choose Get and then Add Extension. Once the add-in says it's installed, you can close this tab.
    Note:
    You may be prompted to enable Sync. This is not needed for the S/MIME extension, and can be enabled or not at your discretion.
  6. Log out of Outlook on the web. Be sure to log out, not just close the window.

Stage 2

  1. Open Edge, and log into Outlook on the web.
  2. Click New message. In the new message window, click the three horizontal dots to the right of "Discard". In that menu, choose Show message options....
  3. In the "Message options" dialog box, check the box for "Digitally sign this message (S/MIME)". Click OK.
  4. Back in the message window, there will be an inline pop-up that says "You can't sign or encrypt this message until the S/MIME extension is installed. To install the extension, click here." Select Click here.
  5. This time, a download will appear. Click the download. You will see an install box that will quickly go away.
  6. Log out of Outlook on the web. Be sure to log out, not just close the window

Stage 3

  1. Open Edge, and log into Outlook on the web.
  2. Click New message. In the new message window, click the three horizontal dots to the right of "Discard". In that menu, choose Show message options....
  3. In the "Message options" dialog box, check the box for "Digitally sign this message (S/MIME)". Click OK.
  4. This time, there should be no inline pop-up, and you can send your message as signed.

Disable your digital certificate

  1. Open Edge, and log into Outlook on the web.
  2. Click the Settings icon (looks like a gear) in the upper right, and then click View all Outlook settings.
  3. Click Mail on the left, and then click S/MIME.
  4. In the "S/MIME" window, uncheck Add a digital signature to all messages I send. Click Save.

This is document bhei in the Knowledge Base.
Last modified on 2022-04-22 16:21:52.