Email Not Received Outside of Website Domain

Hi Everyone,

A website which is in production and on the host's server is able to send and receive emails within its own domain via CI's Email Library, however, the email is not received outside the website's domain. I have tried all sort of configurations, 'mail', 'sendmail', 'smtp'.

The 'To' email address, which is the same as the 'smtp_user' in the Email config, (actual domain redacted), is receiving the emails, which indicates to me that the SMTP is set up correctly.  However the email address the user enters in the site's email form is not receiving the same email; either as an addition in the 'To' list, or as a 'Cc'.

The server host have said that the email application, (CI's Email library), is not authenticating itself, so is being rejected by the likes of Yahoo, Telstra Bigpond etc.

I would have though that the email config I have set up, and is being used would be the authentication:

PHP Code:

$config['protocol'] = 'smtp';
$config['mailtype'] = 'html';
$config['crlf'] = '\r\n';
$config['newline'] = '\r\n';
$config['smtp_host'] = 'domain-name.com.au';
$config['smtp_user'] = '[email protected]';
$config['smtp_pass'] = 'pw';
$config['smtp_port'] = '465';
$config['smtp_timeout'] = '20';
$config['smtp_crypto'] = 'ssl';
$config['charset'] = 'utf-8'; 


Our phones / tablets have been set up with the mail settings, and emails can be received by Yahoo etc.  I do notice in the headers of these emails at Yahoo contain the Sender Policy Framework, and DomainKeys Identified Mail data.  Do the SPF and DKIM need to be added in CI's email config?


Thanks for your help in advance,
Ian.