BuddyPress.org

I don’t know of an existing tool to do this, but you could create it yourself. Use the ‘delete_user’ hook, which fires just *before* the user account is actually deleted; you’ll need to do it this way so that you still have access to the email address. Something like:

add_action( 'delete_user', function( $user_id ) {
    $user = new WP_User( $user_id );
    $email = $user->user_email;
    // ...
} );