sending email codeigniter issue

Question

I am trying to send emails to huge number of users (11000) and I can't send except 300 email per hour so I made that code:

$query_users = $this->db->query('SELECT * FROM `users_list` ');

    foreach ($query_users->result() as $row)
            {
                    $this->email->to($row->email);
                    $this->email->send();

                if($row->id % 300 ==0) { sleep(3600);}  

            }

but I got every hour 300 spam email in my account (as I am sending from it) saying:

A message that you sent was rejected by the local scanning code that checks incoming messages on this system. The following error was given:

This message was classified as SPAM and may not be delivered

Note: when I try to send email to specific person, it's sent correctly. I don't know how to solve this issue, any help?

Answer 1

For the most part, I don't open e-mails where the Subject: field is blank unless I immediately recognize the Sender. Most non-subjected e-mails are spam. Not having a Subject: therefore makes you look spammy and generally will have your e-mail end up in my Junk or Trash folder when it is misidentified as spam.

I had this happen several times the past couple of weeks and when I kindly let those who sent me the e-mails know that they should always use a Subject so they don't look spammy and have spam filters send their e-mail (to me or anyone else) to trash without being read.