No login

From MoodleDocs

The No Login authentication method is for system integration "users", where a user with specific permissions and a scoped web services access is needed, but as an additional security measure they can't log in to the web UI. This is the same concept as "nologin" in Unix, where services need an account to operate but as an additional security measure the system prevents command line access.

To prevent an ordinary user from logging in to the site, No login should NOT be used; instead the account should be suspended by editing the user's profile and checking the 'Suspended account' checkbox. The user will then no longer be able to use web services and they won't receive any notifications.