How to use S/MIME certificate in Outlook on the web and desktop client

[MarcelThieme]

Hi there,

I want to store a s/mime email certificate for a user centrally in exchange online so that it is automatically pulled when I want to use outlook on the web, mobile or desktop. Is this possible at all and if so, where and how do I have to set it up?

I have not found anything in my search so far, I only found this link, but it talks about a local AD, which I do not have.

Any ideas?

[#2]

Hi @MarcelThieme,

If you are using Exchange Online without an on-premises Active Directory (AD), you can still configure and use S/MIME email certificates for users. Here are the short steps:

1. Access the Exchange admin center (EAC):

   • Go to the Microsoft 365 admin center (admin.microsoft.com).
   • Select "Exchange" from the admin centers menu.
     
     

2. Configure S/MIME settings:

   • In the EAC, go to "Mail flow" > "Message encryption" > "S/MIME."
   • Enable S/MIME by checking the "Enable S/MIME signing and encryption" box.
   • Choose the desired options for signing and encryption.
   • Save your settings.
     
     

3. Upload the user's S/MIME certificate:

   • In the EAC, navigate to "Recipients" > "Mailboxes."
   • Select the user mailbox for which you want to upload the S/MIME certificate.
   • Click on "More options" (•••) in the mailbox details pane and choose "Manage S/MIME settings."
   • Use the "Import certificate" button to browse and locate the user's S/MIME certificate file.
   • If needed, enter the certificate password and click "OK" to upload the certificate.

Once the S/MIME certificate is uploaded, you should be able to use it with Outlook on the web, mobile, and desktop clients.

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Kindest regards,

Leon Pavesic

[#3]

Hi Leon,

thanks for your help. I'll test it soon and give you response and mark it as best response and like :-).

Best regards

Marcel

[#4]

Those options don't seem to exist anymore... any update?

[#5]

I found that under Mail flow, the "Message encryption" and "S/MIME" options no longer exist. I cannot find MIME anywhere in the control interface.

Any suggestions are welcome.

[#6]

Hi is this method not available anymore? I can't see these options in my EAC. Is there an alternative method we can use?