Write a book and send it to everyone who is/has been on your server.
Permissions
Permission
Function
easymail.send
Allows users to send mail to one person.
easymail.send.serverwide
Allows users to send server-wide mail.
Metrics
To determine popularity of versions, features, and lingering usage, plugin installs are automatically tracked by the Metrics plugin tracking system. If you don't want to help or are paranoid, edit plugins/PluginMetrics/config.yml and set opt-out to true.