Send Email with Digital Signature in Visual C++ - S/MIME with SHA1, SHA256 and SHA512¶

#include "stdafx.h"
#include <tchar.h>
#include <Windows.h>

#include "EASendMailObj.tlh"
using namespace EASendMailObjLib;

const int ConnectNormal = 0;
const int ConnectSSLAuto = 1;
const int ConnectSTARTTLS = 2;
const int ConnectDirectSSL = 3;
const int ConnectTryTLS = 4;

int _tmain(int argc, _TCHAR* argv[])
{
    ::CoInitialize(NULL);

    IMailPtr oSmtp = NULL;
    oSmtp.CreateInstance(__uuidof(EASendMailObjLib::Mail));
    oSmtp->LicenseCode = _T("TryIt");

    // Set your sender email address
    oSmtp->FromAddr = _T("test@emailarchitect.net");
    // Add recipient email address
    oSmtp->AddRecipientEx(_T("support@emailarchitect.net"), 0);

    // Set email subject
    oSmtp->Subject = _T("email from Visual C++ with digital signature(S/MIME)");
    // Set email body
    oSmtp->BodyText = _T("this is a test email sent from Visual C++ with digital signature");

    // Your SMTP server address
    oSmtp->ServerAddr = _T("smtp.emailarchitect.net");

    // User and password for ESMTP authentication, if your server doesn't
    // require User authentication, please remove the following codes.
    oSmtp->UserName = _T("test@emailarchitect.net");
    oSmtp->Password = _T("testpassword");

    // Most mordern SMTP servers require SSL/TLS connection now.
    // ConnectTryTLS means if server supports SSL/TLS, SSL/TLS will be used automatically.
    oSmtp->ConnectType = ConnectTryTLS;

    // If your SMTP server uses 587 port
    // oSmtp->ServerPort = 587;

    // If your SMTP server requires SSL/TLS connection on 25/587/465 port
    // oSmtp->ServerPort = 25; // 25 or 587 or 465
    // oSmtp->ConnectType = ConnectSSLAuto;

    // Add signer digital signature
    if(oSmtp->SignerCert->FindSubject(_T("test@emailarchitect.net"),
        CERT_SYSTEM_STORE_CURRENT_USER , _T("my")) == VARIANT_FALSE)
    {
        _tprintf(_T("Error with signer certificate; %s\r\n"),
            (const TCHAR*)oSmtp->SignerCert->GetLastError());
        return 0;
    }

    if(oSmtp->SignerCert->HasPrivateKey == VARIANT_FALSE)
    {
        _tprintf(_T("certificate does not have a private key, it can not sign email.\r\n"));
        return 0;
    }

    _tprintf(_T("Start to send email ...\r\n"));

    if(oSmtp->SendMail() == 0)
    {
        _tprintf(_T("email was sent successfully!\r\n"));
    }
    else
    {
        _tprintf(_T("failed to send email with the following error: %s\r\n"),
            (const TCHAR*)oSmtp->GetLastErrDescription());
    }

    return 0;
}