If you have ever opened the Windows 10 Mail app settings, you may have noticed the Email security option on the Settings pane. For most users, clicking on it displays “This setting can’t be applied to any of your accounts” message. Over the years, several Windows 10 users have asked us what Email security feature in the Mail app is, why it cannot be applied to some accounts, and how to enable the feature. In this guide, we will discuss what Email security in the Mail app is. Why is Email security not available for your email account? According to Microsoft, the Email security in the Windows 10 Mail can be applied or used only for S/MIME (more on this later) enabled accounts. That is, Email security can’t be applied to a personal or standard email account. In short, the Email security in the Mail app is not available for most PC users, and there is no way to enable the Email security settings for standard email accounts. In other words, “This setting can’t be applied to any of your accounts” message indicates that you are using a standard email account like most PC users out there. What is S/MIME? S/MIME stands for Secure/Multipurpose Internet Mail Extensions. The S/MIME standard or certificate adds an additional layer of security for emails sent to and received from an email account. Using this, users can digitally sign and encrypt messages. Note that one can’t use S/MIME digital signing and encryption with a personal account. Enable Email security settings in Windows 10 If you have an S/MIME enabled Exchange account, you can enable and configure Email security settings in the Mail app. Here is how to do that. Step 1: Open the Mail app. Click on the settings/gear icon on the left pane to open the Settings pane. Step 2: Click on the Email security to view all available options. As you can see in the picture below, the Mail app offers digital signature and encryption. Select an account and then change digital signature and encryption settings.