It would be nice if there was an option to avoid duplicative notifications fired by multiple actions for the same event to the same user.

For example, a trigger "Host unreachable" goes to PROBLEM state and causes two different actions to fire:

1. Send message to user group Tech Support
2. Send message to user group System Administrators

If some user "A" is part of these two groups, then he/she will be notified twice for this event.

Proposed solution is to make Zabbix detect such scenarios and send only one notification. Perhaps it can be achieved by recording all event IDs that the user was already notified about and not sending the duplicative notifications to the same media.

A "notify only once" setting could also exist for enabling/disabling this functionality.

Without this functionality one has to come up with sophisticated action settings to avoid multiple notifications for the same event.