Question
Is there a cPanel notification for "Maximum percentage of failed or deferred messages"?
Answer
Unfortunately, cPanel does not provide a notification template for when the "failed or deferred" messages limit has been reached.
The sending user will receive a bounced notifying the occurrence and the server administrator should be contacted to further investigate the issue.
Further information about specific alerts and templates can be found in the following documentation link: https://docs.cpanel.net/knowledge-base/general-systems-administration/notification-templates/86/