When running a multi-author site in WordPress, some of your authors may not be familiar with the featured image functionality.
In this case, you may want to remind yourself or your users to upload a featured image whenever they are submitting a post in WordPress.
You can do this by installing and activating the Require Featured Image plugin.
Once activated, the plugin will display a notification box in the post edit area, informing users that this post requires a featured image.
You and your users will be able to save posts as drafts, but you cannot publish the post until you add a featured image.