If you configure a notification for an internal event when an item becomes not supported, the notification doesn't include the reason why an item became unsupported. To see the reason, you either need to check the Zabbix frontend before and item becomes supported again, or read the Zabbix server log. This isn't very convenient, since you have to do one step further to find out what is the reason for an item to become not supported.

There should be a macro which holds the information about the not supported reason, so that it can be inserted into the notification message.