To make Permalink Manager compatible with Postie plugin, you will need an additional code snippet. After the new post is created, the custom permalink will be regenerated and a final title and slug will be used in the URI.
function pm_regenerate_the_permalink($post) { global $permalink_manager_uris; // Get the default custom permalink based on a permastructure set with Permalink Manager if(!empty($post->ID)) { $permalink_manager_uris[$post->ID] = Permalink_Manager_URI_Functions_Post::get_default_post_uri($post->ID); // Save the update update_option('permalink-manager-uris', $permalink_manager_uris); } } add_action('postie_post_after', 'pm_regenerate_the_permalink', 99);