On the "Feature Activation" screen, you can disable and enable again some features.
You can also configure the E-mail Notifications setting.

Only System Administrators and Kintone Administrators can open the "Feature Activation" screen.

The steps are as follows.

1. Click the Settings button on the upper right side of the Kintone screen and click "Kintone Administration."
   Reference: Opening the Kintone Administration Screen

2. Click Feature Activation in the Other category.

The "Feature Activation" screen opens.
The following describes the overview of each setting option.

The E-mail Notifications feature is a feature to send Kintone notifications via e-mail. This feature enables users to check notifications via e-mail in addition to checking them on Kintone.
By default, the feature is enabled and "To Me" notifications are sent to users via e-mail in HTML format.
For details on the setting options, refer to Settings to Activate E-mail Notifications.

• Activate Spaces
  You can configure whether to enable the Space feature.
  When the check box for this feature is selected, you can choose to enable or disable the Allow users to create apps that do not belong to any space option.
  
  
• Activate Guest Spaces
  If the check box for Activate Spaces is selected, you can configure whether to use the Guest Space feature.
  
  
• Activate People and Private Messages
  You can configure whether to use the People and Private Messages features.

This is a setting option that enables you to configure whether to allow users to create apps that do not belong to any space.

Apps are placed either on Portal (top page) or in a space. "Apps that do not belong to any space" refer to the apps that are placed on Portal.

• If you check this check box:
  Users can create both apps that belong to a space (in-space apps) and those that do not belong to any space.
  
  
• If you uncheck this check box:
  Users are only able to create apps that belong to a space (in-space apps). Users cannot create apps that do not belong to any space. Unchecking this check box will not affect existing apps.
  

An app group is always set for an app. When you create an app, the app group specified as the Default App Group is automatically set for the app, though it is also possible to change the app group for this app. However, the "Public" app group is always set for the apps that belong to a space (in-space apps), and you cannot change the app group for these apps.

If you uncheck Allow users to create apps that do not belong to any space, users will only be able to create apps that belong to a space (in-space apps). This means that apps created will always belong to the "Public" app group, and you cannot change the app group for the apps. In other words, if you uncheck Allow users to create apps that do not belong to any space, it means that you will not allow users to create apps that do not belong to the "Public" app group (including the apps that belong to the "Private" app group).

If you are using some apps that belong to an app group other than the "Public" app group, please take this into consideration before configuring the setting.