By default, WordPress lacks the ability to send emails to registered users. This plugin was created to fill the gap by allowing you to send emails to your blog users.
More details are available on the WordPress Send Private Email plugin page on my blog.
To prevent abuse this powerful mass mailing functionality is available only to users with Administrator role. This can be changed quite easily if need be, for instance to allow all Editors or greater to use the plugin. Just let me know if you need it, and I’ll modify it for you.
Once activated it adds a new submenu called Write Private Email under the Write menu in the blog management area.
Simple, powerful and very convenient to use.