Alerts are sent when the job is generating the issue, so each job on each server needs to be checked. Since one sends every minute, are you sure there aren't a few jobs asking for media? Each job should send the media alert only once, not repeatedly. Now, you may have set up Error Handling rules to auto answer the alert, which would explain the every minute email issue since every time the error handling answered OK to the alert, the job would then send another alert since the new media was not inserted.
You can also you the "circuit breaker" feature for notificatiosn so you are not bombarded with emails. Verifyt he above issue first of course since this fix will limit your notifications. On your recipient properties page, you will see the section titled "Limit the number of notifications sent" This is the circuit breaker feature, since once x number of alerts are received, it shuts done notifications to that recipient for x amount of time. (like a power circuit shutting down after a surge until it is reset)
The Maximum number of times in within x amount of minutes is a moving window, so it deals with X amount of time, regardless of exact minutes alerts are received. IE: you receive an alert at 9:00am, and 4 more at 9:06am. If you had a max of 5 alerts in a 5 minute window, this would not shut your notifications down. However, if you receive another alert at 9:10am, your alert notifications would be suspended since you have 5 alerts in the time window (9:06a - 9:11a) Notifications would turn back on for your recipient when you "Reset time value is reached, ie 15 minutes later. Generally, the 5/5/15 defaults are good, modify as needed.