Maybe this helps,
I used the “Get Code” and copied that code in to “functions.php”.
Removing that code from “functions.php”, and newsletter sign was gone.
add_action('init', 'cptui_register_my_cpt_newsletter');
function cptui_register_my_cpt_newsletter() {
register_post_type('newsletter', array(
'label' => 'Newsletter',
'description' => '',
'public' => true,
'show_ui' => true,
'show_in_menu' => true,
'capability_type' => 'post',
'map_meta_cap' => true,
'hierarchical' => false,
'rewrite' => array('slug' => 'newsletter', 'with_front' => true),
'query_var' => true,
'exclude_from_search' => true,
'menu_position' => '6',
'supports' => array('title','editor','excerpt','trackbacks','custom-fields','comments','revisions','thumbnail','author','page-attributes','post-formats'),
'labels' => array (
'name' => 'Newsletter',
'singular_name' => 'Newsletter',
'menu_name' => 'Newsletter',
'add_new' => 'Add Newsletter',
'add_new_item' => 'Add New Newsletter',
'edit' => 'Edit',
'edit_item' => 'Edit Newsletter',
'new_item' => 'New Newsletter',
'view' => 'View Newsletter',
'view_item' => 'View Newsletter',
'search_items' => 'Search Newsletter',
'not_found' => 'No Newsletter Found',
'not_found_in_trash' => 'No Newsletter Found in Trash',
'parent' => 'Parent Newsletter',
)
) ); }