NextcloudPi Smartmontools email Notifications - Odroid HC2?

just wondering how to configure Smartmontools “smartd” to send me email notifications in case of HDD failure?
It looks like i need a mailserver but Postfix is already installed with my NextcloudPi image on Odroid HC2 (and already configured for nextcloudPi mail probably?..)
Well i don’t want to mess up my NextcloudPi installation for this, but Smartd email notifications
would be great.

If anyone have a tutorial?
(otherwise Smartmontools works nicely on my Odroid HC2 when i’m starting it manually)