To get rid of the error, you should follow the steps below:
Also, if you have updated your operating system, perhaps the update can break the installation or reset some settings. If you haven’t installed S/MIME firstly, it cannot work and shows the error message.
Fixes for S/MIME Control Isn’t Available Install S/MIME Now, let’s see them in the following part. Fortunately, you can try some methods to easily fix the issue. This error always happens on your Internet Explorer in Windows 10/8/7. Then, you can’t open emails or download attachments. You may receive a common error saying “the content can't be displayed because the S/MIME control isn't available”.
