During each analysis, the notifications are computed for each user who has subscribed to notifications. Then, in an asynchronous way, these notifications are sent to users by emails.
To set the delay between processing of notification queue, set the
sonar.notifications.delay property (in seconds) in SONAR_HOME/conf/sonar.properties. Note that the server has to be restarted for the new value to be taken into account.
To be able to send notifications by email, go to Settings > General Settings > General > Email and configure the email settings.