--- features: - This feature is the third part of subscription confirmation feature. Support to send email to subscriber if confirmation is needed. To use this feature, user need to set the config option "external_confirmation_url", "subscription_confirmation_email_template" and "unsubscribe_confirmation_email_template". The confirmation page url that will be used in email subscription confirmation before notification, this page is not hosted in Zaqar server, user should build their own web service to provide this web page. The subscription_confirmation_email_template let user to customize the subscription confimation email content, including topic, body and sender. The unsubscribe_confirmation_email_template let user to customize the unsubscribe confimation email content, including topic, body and sender too.