If you have Board Following enabled, you can filter the text of the email that is sent to followers whenever a new topic is posted on a board.
In your functions.php file, or other suitable place, add the following:
/**
* Filter the notification email text to followers of a board
* @param $message - the original email content
* @param $post - the post object for the new topic
* @board_id - the ID of the board posted on
*/
function your_prefix_notification_email_content( $message, $post, $board_id ) {
// Add your new message content here
$message = 'My new message';
return $message;
}
add_filter( 'ctdb_follower_notification_new_topic_email', 'your_prefix_notification_email_content', 10, 3 );