Cannot send mail via SMTP (version 3.16)

@Rifky Pujiyansyah Suropaty

If PHPMailer works, you may try this library of mine, it extends CI_Email: https://github.com/ivantcholakov/codeigniter-phpmailer
Just install it within your application and write/use your configuration data. You would not need to change your application code for sending emails, leave it as it is, in CodeIgniter style. Thus PHPMailer would do the job hidden behind the CodeIgniter's API.

Second, not mandatory: It would be better, if you try to use tls (port 587), it is a newer way encryption that is also supported by Gmail.