You must turn on the “less secure apps” function if you are using gmail. Please reference the following document: https://support.google.com/a/answer/6260879?hl=en
Select “Function Panel” on the main page after logging in. After selecting “Function Panel”, select “E-mail” under the Network
setting.
On the E-mail setup page, please enter the necessary information as requested. Please refer to E-mail provider’s setup pages to find the correct SMTP and Port numbers as they will be different from provider to provider. It is strongly suggested to create an E-mail account specifically for the recorder and to have the recorder’s email address, send it to the primary recipient that would like to receive the notification.
Select “Edit Recipient” after entering the necessary information. Please add a recipient email address and the scheduled time frame (default is 24x7). You may test the recipient’s email account to confirm that the sender and receiver email address are set up correctly.
If you receive failure messages please log in to the gmail account as the first account and click the link: https://accounts.google.com/b/0/DisplayUnlockCaptcha to unlock the account