We recommend managing renewal notifications per certificate. See Disable renewal notices for a discovered certificate.
In your CertCentral account, go to Settings > Notifications.
On the Notifications page, on the Notification settings tab, expand Advanced notification settings.
Scroll down the page, under Other renewal notifications, unselect Turn on for discovered non-DigiCert certificate.
Select Save Settings.
Discovery will no longer send renewal notifications for expiring discovered SSL/TLS certificates.