Sending email from office365 sometimes not working - php

Question

I've setup my email sender using outlook office365 with codeigniter 3. Below code works but sometimes it doesn't and I don't know why. Sometimes it will not work the first time I push my repo but when I tried it again, it works. I've logged the error below.
Error:
Failed to authenticate password. Error: <br />Unable to send email using PHP SMTP. Your server might not be configured to send mail using this method.<br />
Code:
public function send_mail($to_email = null, $name = '')
{
$config = array(
'protocol' => 'smtp',
'smtp_crypto' => 'tls',
'smtp_host' => 'smtp.office365.com',
'smtp_port' => 587
'smtp_user' => EMAIL_SENDER,
'smtp_pass' => EMAIL_SENDER_PASSWORD,
'mailtype' => 'html',
'charset' => 'utf-8',
'wordwrap' => TRUE,
'newline' => "\r\n",
'crlf' => "\n",
'starttls' => true
);
$from_email = EMAIL_SENDER;
$this->load->library('email', $config);
$this->email->set_newline("\r\n");
$this->email->from($from_email, 'Power App');
$this->email->to($to_email);
$this->email->subject('Password Reset');
$this->email->set_crlf("\r\n");
$data["user"] = $to_email;
$data["name"] = $name;
$this->email->message($this->load->view('email/email_reset_password_template', $data, true));
//Send mail
if ($this->email->send())
return "Email sent successfully.";
else {
return $this->email->print_debugger();
}
}
UPDATE:
Its now always working when I use PHPMailer. Haven't really discover why its not always sending email using email library.