Multisite

Network-activate it and every site is set up, including sites added afterwards. Each site has its own settings, its own log, its own daily sign-in check, its own From domain check and its own alert address, if it posts alerts. Each site is judged by its own address when it decides whether it is a copy and holds its email. The mail connection set in wp-config.php applies to every site, and a must-use plugin can give one site its own (see Setting the connection in wp-config.php). While the plugin is network-activated, a site deleted from the network takes its log with it. A site deleted while the plugin was switched on for that site alone leaves its log behind at the time, and deleting the plugin clears those leftovers away.