So, the SMS message is going to come from the 'Execute program : powershell.exe ... "C:\Alert_Scripts\SMS_Alert.ps1" action. This action is called for both your trigger and reset
This would be a custom powershell script written by somebody in your organisation. I would suggest reviewing this powershell script if necessary.
When an event occurs (node down), if an associated alert action exists (i.e. email, write to solarwinds event and then execute a program when said node goes down) then only the main action will be notified in your event logs (node down) and only the name of the alert action 'KA: Alert me when a node goes down' will appear in your alerts log.
To my knowledge, solarwinds is unlikely to know about the triggering of the powershell script, or receive any direct results. That powershell script will trigger a SMS to be sent via the necessary equipment with values passed from your solarwinds server.
We only write to the event log and email out.
