Filter: postie_parent_post

This filter is called to determine if there should be a parent post.
  • $parentid – an integer which is the post ID that Postie thinks should be the parent. If Postie doesn’t think there is a parent the value will be NULL.
  • $email – the parsed email
add_filter('postie_parent_post', 'my_postie_parent_post', 10, 2);

function my_postie_parent_post($parentid, $email) {
    return $parentid; 

Available starting in version 1.9.27