Sign in with Microsoft
Sign in or create an account.
Select a different account.
You have multiple accounts
Choose the account you want to sign in with.


This update fixes the following issues that you may experience when you use the S/MIMIE encryption in the Outlook on the web client (previously known as Outlook Web App) in Microsoft Exchange Server 2016:

  • When you access a mailbox that's hosted on a computer by using the Outlook on the web client that has the S/MIME control installed, you may receive the error message "Your S/MIME control is out of date. You must reinstall it." In addition, this issue persists even if you reinstall the S/MIME control.

  • You can't send an S/MIME signed or encrypted email message in the Outlook on the web client. In addition, you may receive the error message "An error occurred while encoding this S/MIME message. An unexpected S/MIME error occurred." especially when you rehydrate a draft, compose the email message for more than a minute, or add attachments or images to the message.

How to get this update

To get this update, install Cumulative Update 11 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.

After you install the S/MIME control update, when you open the Outlook on the web client in Internet Explorer for the first time, you are prompted with the following message:

Do you want to allow the domain <owa website> to use the S/MIME control to encrypt and decrypt messages in your inbox? Only allow domains that you trust. If you select Yes, you won't be prompted again for this domain. If you select No, the domain won't have access to S/MIME.

When it's shown, click Yes to trust the domain.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Learn about the terminology that Microsoft uses to describe software updates.

Need more help?

Want more options?

Explore subscription benefits, browse training courses, learn how to secure your device, and more.

Communities help you ask and answer questions, give feedback, and hear from experts with rich knowledge.

Was this information helpful?

What affected your experience?
By pressing submit, your feedback will be used to improve Microsoft products and services. Your IT admin will be able to collect this data. Privacy Statement.

Thank you for your feedback!