Email Alerts are set up so that if any of the other integration options fail at any point an email is sent to recipients of the client's choosing notifying them of the failure. This is an all or nothing feature, if turned on it will work for all enabled integration options. If turned off it will not work for any of the integration options.

It is especially useful for document uploads and processing because if one file fails we still attempt to process all other files, and the overall job will not fail. 

Standard Mail Settings are only required if Email Alerts will be enabled. Custom SMTP Settings are required either way because turning the Email Alerts on or off is contained in these settings.

To configure this feature you will need to set up both: Standard Mail Settings and Custom SMTP Settings

If this integration option is enabled
 App Settings will also need to be set up.