Sending Bulk Emails when a new post is published in WordPress

function userNotification($post_id) {
	
 global $wpdb;
	
 $post = get_post($post_id);
 
 //$usersarray = $wpdb->get_results("SELECT user_email FROM $wpdb->users;");
 
 //$users=array();
 //foreach($usersarray as $user){
 //$users[]=$user->user_email;
 //}
 
 //$userarray = implode(",", $users);
 
 //Getting emails from formidable form

//it.form_id is the field name
$items = FrmEntry::getAll(array('it.form_id' => 4));

$emails=array();
foreach($items as $item){
$emails[]="Bcc: ".FrmProEntriesController::get_field_value_shortcode(array('field_id' => 34, 'entry' => $item->id));
}

//$userarray = implode(",", $emails);
   
 if (!(defined( 'REST_REQUEST') && REST_REQUEST )) { 
   
   $subject = $post->post_title;
   $content=$post->post_content;
   $content=$content."<p>Article link at <a href=".get_permalink( $post_id ).">Link to article post</a></p>";
   
   $headers = array('Content-Type: text/html; charset=UTF-8');



   foreach($emails as $email){
   $headers[]=$email;}
   
   wp_mail("",$subject,$content,$headers);
}
}

add_action('publish_post', 'userNotification',10);