When checking Thresholds, if a Data Source returns Unknown Data ('U'), consider the value as zero for the Threshold check. You can also enable log this issue.
Checking this box will switch Thold from performing inline Notification to using either the Notification Daemon, or notifications performed out of band by the Notification poller.
Check this box if you wish Warning Notification List recipients to receive Alert Emails in addition to the Alert Notification list receivers.This case is applicable when Warning Notifications goes to Administrators and Alert Notifications go to Management.