As documented in example.scrutiny.yaml there are multiple ways to configure notifications for Scrutiny.
Under the hood we use a library called Shoutrrr to send our notifications, and you should use their documentation if you run into any issues: https://containrrr.dev/shoutrrr/services/overview/
While the Shoutrrr library supports many popular providers for sending notifications Scrutiny also supports a "script" based notification system, allowing you to execute a custom script whenever a notification needs to be sent. Data is provided to this script using the following environmental variables:
SCRUTINY_SUBJECT - eg. "Scrutiny SMART error (%s) detected on device: %s"
SCRUTINY_DATE
SCRUTINY_FAILURE_TYPE - EmailTest, SmartFail, ScrutinyFail
SCRUTINY_DEVICE_NAME - eg. /dev/sda
SCRUTINY_DEVICE_TYPE - ATA/SCSI/NVMe
SCRUTINY_DEVICE_SERIAL - eg. WDDJ324KSO
SCRUTINY_MESSAGE - eg. "Scrutiny SMART error notification for device: %s\nFailure Type: %s\nDevice Name: %s\nDevice Serial: %s\nDevice Type: %s\nDate: %s"