Mass Mail allows to wp bloggers to send mass mails to users groups.
= How can I be sure that is working correctly?
Check your smtp server and see if it is started.
= How can I configure it?
= How can I configure Sender email?
= How can I change to what group I send?
You should check you wordpress database and select the table you wanna send mass email, put the name of the table and the name of the table email field and click Save & Send Mails ->