You had better use gmail, not yahoo or hotmail.
1. Please make sure DVR or NVR has connected to router and Internet successfully. You can judge by picture below. If it always keeps disconnected, please click here to get some help. /kb/content/10/87/what-to-do-if-dvr-or-nvr-can-t-connect-cloud.html
2. Please enable alarm and email alerts function.
3. Please log in your gmail account.
4. Please open website below
5. Please tick turn on.
6. Please set up email in DVR setting like picture below. If mail test succeeds, it is working.
smtp server is smtp.gmail.com
port is 465
user name is your gmail account
password is your gmail account password
sender is your gmail account
receiver can be any email.