add_filter( 'mailster_auto_post', function ( $data, $post ){
    //Get Author ID
    $author_id=$post->post_author;
    //Get the categories
    $categories = get_the_category( $post->ID );
    $data['title'] = array(
             $post->post_title,
             get_the_author_meta( 'display_name', $author_id ),
             $categories->name,
     );
     return $data;
}, 10, 2 );