In On-Premises mode the follow-up action "Send an e-mail alert" needs to be defined in the on-premises application server's registry.
When you create a trigger alert with the follow-up action "Send an e-mail alert", the e-mail is sent from our cloud servers, in the Online Mode. But in On-Premises Mode which functions only locally, the administrator needs to define his local SMTP server in order for this follow-up action to work.
In order to define your local SMTP server, please open the regedit.exe on the On-Premises server and go to HKEY_LOCAL_MACHINE\SOFTWARE\Smart-X\ControlUp\SMTPSettings and define the needed details, such as:
SenderEmail, ServerName, EnableSSL, Port etc.