SSL operation failed with code 1 Codeigniter does not send email
This might help someone in the future.
Even if every credential is right, some antivirus or firewall installed in the machine might prevent sending email thru SMTP. Temporarily disabling the antivirus or firewall to check is a good idea.
In my case, Avast antivirus caused this issue, and disabling this resolved my problem.
To disable Avast intercepting SMTP, unchecking Scan outbound emails (SMTP) checkbox will do the trick.
