Please ensure you have the correct settings entered in your SMTP page on your LILIN device, to verify these settings simply log in to your Gmail account.
Next, go to google.com and search -
'Less Secure Apps - Google'
Now, log in to your google account and 'Enable' access for less secure apps. This will now allow your LILIN device to use your Gmail account to send email alerts and alarm notifications
If emails are still never received please also follow the guide here