Notify Failing Status Checks is an Always Be Closing (ABC) feature that posts a comment on a pull request whenever a commit status has a failure or an error. This will send an email to anyone watching the pull request and notify them of the commit status.
Most continuous integration tools can be configured to send a notification email to the owners of the GitHub repository. But they do not send an email to the author of the pull request. When was the last time that you submitted a patch to someone else’s repository, you check back a week later when you don’t hear any feedback from the maintainers and that’s when you discover that one or more tests are failing? The ABC service will immediately notify you of those failing status checks.