If you want the system to notify you by email about trigger execution errors, you need to define a default email account used to send system notifications, such as errors occurring during automatic process execution.
Go to the OPTIONS system menu and, on the Configuration tab in the Triggers section, fill in the Email account field.
If you do not have any SMTP connections defined yet, create a new connection by clicking the New… button, or do so in the Connection to sources/destinations.