D-Link DNS-320L User Manual page 189

Section 4 - Configuration
Receiver Enter the e-mail address you want to send the alerts to. This address must correspond with the SMTP server
E-mail: configured above.
Secure Select STARTTLS or SSL from the drop-down menu if it is required by your SMTP server, or select NONE.
Connection:
Click the Test E-Mail button to send a test alert and confirm that your settings are correct.
Test E-Mail:
D-Link ShareCenter DNS-320L User Manual 183