email send error

I developing a website, where in an admin page have a button which processing an email send (to admin).

This is the configuration:

PHP Code:

   $this->load->library('encrypt');
    $config = array(
        'protocol' => 'smtp', // 'mail', 'sendmail', or 'smtp'
        //'useragent' => 'CodeIgniter',
        'smtp_host' => 'smtp.mail.yahoo.com',
        'smtp_port' => 465,
        'smtp_user' => '****',
        'smtp_pass' => '****',
        'smtp_crypto' => 'ssl', //can be 'ssl' or 'tls' for example
        'mailtype' => 'html', //plaintext 'text' mails or 'html'
        'charset' => 'iso-8859-1',
        'wordwrap' => TRUE,
    );
    $this->load->library('email', $config); 


I try with different configurations:

• gmail with SSL, with TLS, with different 'smtp_host' like with and without ssl://
  
• different gmails with @gmail.com and with another one which is not @gmail.com
  
• yahoo mail with ssl
  
• different PHP versions like 5.6 and 7.1
  
• enable less secure apps in gmail/yahoomail
  

And this is the function:

PHP Code:

 public function send_email(){
    $from = $this->config->item('smtp_user');
    $to = '****';

    $this->email->from($from);
    $this->email->to($to);
    $this->email->set_newline("\r\n");
    $this->email->subject('szerkesztési jog igénylése');
    $this->email->message(
      'Tisztelt adminisztrátor!\r\n
      \r\n
      Egy felhasználó szerkesztési jogot szeretne igényelni a Faipari szakszótárhoz\r\n
      Kérjük jelentkezz be, és bíráld el a szerkesztési jogát az igénylőnek'
    );

    if ($this->email->send()) {
      $this->session->set_flashdata('uzenet', 'Sikeres szerkesztési jog igénylés');
      redirect('pages/user', $data);
    } else {
      show_error($this->email->print_debugger());
    }
  } 


I got different error codes for different cases, but nothing made solution after few hours google search and reading threads.


With yahoo/ssl:

Severity: Warning
Message: fsockopen(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
Filename: libraries/Email.php

Severity: Warning
Message: fsockopen(): Failed to enable crypto

Severity: Warning
Message: fsockopen(): unable to connect to ssl://smtp.mail.yahoo.com:465 (Unknown error)

The following SMTP error was encountered: 0
Unable to send email using PHP SMTP. Your server might not be configured to send mail using this method.

With gmail/ssl:

A PHP Error was encountered
Severity: Warning
Message: fsockopen(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

With gmail/tls:

A PHP Error was encountered
Severity: Warning
Message: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

An Error Was Encountered
220 smtp.gmail.com ESMTP u9sm5539564wmd.14 - gsmtp

Have you any idea what can solution this problem? My codeigniter version is 3.1.7

Does your server have a SSL certificate in place?