Currently there a variety of situations when emails are not sent. With the default LBackup example configuration emails are only sent out if the backup has actually started. If a machine is not available for backup then this will not generate an email report. For automated notifications regarding these situations you should schedule the lmail program at a specific interval to report the status of the backups. Another possibility is to enable more verbose email reporting within the LBackup configuration file.
There is a configuration option which you may set so that every time a backup configuration is executed an email is sent out regardless of the success or failure of the backup. Please examine the example lbackup configuration included in the /lbackup directory.
This would ensure that only one email can be sent at a time. This is currently a low priority.
This would ensure that emails are only sent when a backup is not in progress. This feature is debatable and requires requires further discussion.