Email smtp configuration with security certificates

Getting the error while tesing the email alert notification-
grafana-server: t=2019-11-25T11:16:10+0100 lvl=eror msg=“Failed to send alert notification email” logger=alerting.notifier.email error=“Could not load cert or key file. error: open : no such file or directory”
grafana-server: t=2019-11-25T11:16:10+0100 lvl=eror msg=“failed to send notification” logger=alerting.notifier uid= error=“Could not load cert or key file. error: open : no such file or directory”

cert and key file are readable and have permissions.