Changed Backup Interval and Notifications emails won't stop

I recently changed all of the intervals for backups to happen at a reduced interval, and since then I have been receiving these emails for every client, every day:

File backup status for client "client-name" is back to ok. Alert was sent because there was no recent backup in the last 6

Also these:

No recent file backup for client "client-name". Last file backup was 6h ago. This alert is sent if there is no recent backup in the last 6h and then repeated every 10h while there is no successfull backup.

How do I get rid of these notifications?