When you email from CodeIgniter SMTP credential and server error like SSL3_GET_SERVER_CERTIFICATE:certificate verify failed then you should follow below step.
Donwload http://curl.haxx.se/ca/cacert.pem and move to .pem file to C:\xampp\apache\conf\cacert.pem
Change in php.ini file
Make sure
extension=php_openssl.dll
[openssl]
openssl.cafile=C:\xampp\apache\conf\cacert.pem
Restart apache server
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