CODE EXAMPLE FOR PHP

Expected response code 250 but got code "530", with message "530 Must issue a STARTTLS command first. "

//encrytion should be set while using email library
$transport = (new Swift_SmtpTransport($smtp_server, $smtp_port))
                        ->setUsername($smtp_username)
                        ->setPassword($smtp_password)
                        ->setEncryption('tls');  //important to set encryption here.