CodeIgniter Email not being received - codeigniter

Question

I currently have a contact form on my website which sends off an email notification upon submission. It is working perfectly on my end and even when I send it externally to friends as a test they are receiving it.
My client however, who is in France, can't seem to receive this email at all and I have no idea why. Is there anything I need to do to ensure that they receive it? I thought it was something on their end but they're absolutely adamant that it's not and that it's a problem with my code. I have tried different email addresses for them with different domains and still no luck!
$this->load->library('parser');
$config['mailtype'] = 'html';
$config['charset'] = 'utf-8';
$this->load->library('email');
$data = array(
'first_name' => $this->input->post('first_name'),
'last_name' => $this->input->post('last_name'),
'email' => $this->input->post('email'),
'phone' => $this->input->post('phone'),
'message' => $this->input->post('message')
);
$body = $this->parser->parse('html_email', $data, true);
$this->email->from('test#test.com', 'Duparc');
$this->email->to('test#test.com');
$this->email->subject('Test Email');
$this->email->message($body);
$this->email->send();

Answer 1

In my opinion the problem does not originate from CodeIgniter. Assuming the mail did not went into a spam box, your customer's provider is probably dismissing your message for some other reason. One reason I can immediately think of is that you are probably trying to send a message from a domain (e.g. test.com) you're not allowed from. My advise is starting to try sending an email with another tool to your french customer (any sendmail or postfix client tool) and to see if he do receive it.
If that succeeds, then the problem probably comes from your forged email (therefore try using a valid domain name). Sometimes removing it completely will work too (it might then be replaced by the external IP).
If not, then the problem comes from your web server's config. I had this problem using postfix where I had to explicitly set the "General Options" > "What domain to use in outbound mail" configuration option to my domain name in order to be accepted by a capricious server which silently dismissed our mail.
If nothing is working, you might also use another mail server which might luckily fix the issue. Here is the code I used to force CodeIgniter using sendmail instead:
$config['protocol'] = 'sendmail';
$config['mailpath'] = '/usr/sbin/sendmail';
$this->email->initialize($config);