Mass Messaging in Buddypress is a plugin by ElbowRobo for Buddypress, it adds a dashboard menu and a tab in the messages section. Once you navigate into the messages section and click the “Mass Messaging” tab you have access to all the options which you chose in the dashboard.
Including mass messaging to:
Members
Members of Groups
Members of Events (EventPress)
And: * Select all buttons to allow mass messaging to all members easily.
In this page you also see ‘subject’ and ‘description’ just like on the Buddypress compose page.
Download and info: http://wordpress.org/extend/plugins/mass-messaging-in-buddypress/