Adding Specific Configuration in CodeIgniter Email Class

I don't remember whether the original CodeIgniter's email library can do this, but it can be upgraded to use PHPMailer. You may try this project of mine https://github.com/ivantcholakov/codeigniter-phpmailer , the README contains instructions about the installation.

Your application code about emails would not need modifications, leave it as it is.

Then, see the answer of this question: https://github.com/ivantcholakov/codeign.../issues/14
A new configuration option has been added that is interesting for you, $config['smtp_conn_options'] .