Please refer to these steps below.
1. Please make sure your DVR system is connected to the internet
2. Please Enable alarm and tick the 'Send Email'.
3. Please log in your Gmail account.
Please tick turn on "Access for less secure apps"
4. Please set up email in recorder setting like the picture below.
If you click 'Mail testing' shows Test success, it is working.
'Smtp server' is smtp.gmail.com
'Port' is 465 or 587 that follow your email setting
Enable 'Need SSL' that follow your email setting
'User Name' is your Gmail address
'Password' is your Gmail account password
'Sender' is your email address
'Receiver' can be an email that you want