Download/Retrieve Email from Gmail account in Visual C++

In previous section, I introduced how to retrieve email over SSL connection. In this section, I will introduce how to download email from your Gmail account in Visual C++.

Introduction

Gmail POP3 server address is pop.gmail.com. It requires SSL connection on 995 port, and you should use your Gmail email address as the user name for user authentication.

Gmail IMAP4 server address is imap.gmail.com. It requires SSL connection on 993 port, and you should use your Gmail email address as the user name for user authentication. For example: your email is gmailid@gmail.com, and then the user name should be gmailid@gmail.com.

To retrieve email from Gmail account, you need to enable POP3 or IMAP4 access in your gmail account settings.

Because Gmail POP3 server doesn’t work like normal POP3 server, it hides old emails automatically even the email was not deleted, so we suggest that you use IMAP4 protocol.

Server Port SSL Protocol
pop.gmail.com 995 SSL required Pop3
imap.gmail.com 993 SSL required Imap4 (recommended)

Important

If you got authentication error, you need to enable Allowing less secure apps or Sign in using App Passwords.

Another way is Gmail OAUH, please see Gmail IMAP OAUTH section.

Note

Remarks: All of examples in this section are based on first section: A simple Visual C++ project. To compile and run the following example codes successfully, please click here to learn how to create the test project and add reference to your project.

[Visual C++ Example - Retrieve email from Gmail account]

The following example codes demonstrate how to download email from Gmail account using IMAP4 protocol.

Because Gmail POP3 server doesn’t work like normal POP3 server, it hides old emails automatically even the email was not deleted, so we suggest that you use IMAP4 protocol.

Note

To get the full sample projects, please refer to Samples section.

#include "stdafx.h"

#include "eagetmailobj.tlh"
using namespace EAGetMailObjLib;

int _tmain(int argc, _TCHAR* argv[])
{
    const int MailServerPop3 = 0;
    const int MailServerImap4 = 1;
    const int MailServerEWS = 2;
    const int MailServerDAV = 3;

    // Initialize COM environment
    ::CoInitialize( NULL );

    // Create a folder named "inbox" under current exe file directory
    // to save the emails retrieved.
    TCHAR szPath[MAX_PATH+1];
    memset( szPath, 0, sizeof(szPath));
    ::GetModuleFileName( NULL, szPath,  MAX_PATH );

    // Change file name to current full path
    LPCTSTR psz = _tcsrchr( szPath, _T('\\'));
    if( psz != NULL )
    {
        szPath[psz-szPath] = _T('\0');
    }
    TCHAR szMailBox[MAX_PATH+1];
    memset( szMailBox, 0, sizeof(szMailBox));
    wsprintf( szMailBox, _T("%s\\inbox"), szPath );

    // Create a folder to store emails
    ::CreateDirectory( szMailBox, NULL );

    try
    {
        IMailServerPtr oServer = NULL;
        oServer.CreateInstance(__uuidof(EAGetMailObjLib::MailServer));

        // Gmail IMAP4 server address
        oServer->Server = _T("imap.gmail.com");
        oServer->User = _T("gmailid@gmail.com");
        oServer->Password = _T("testpassword");
        oServer->Protocol = MailServerImap4;

        // Enable SSL connection
        oServer->SSLConnection = VARIANT_TRUE;

        // Set 993 IMAP4 SSL port
        oServer->Port = 993;

        IMailClientPtr oClient = NULL;
        oClient.CreateInstance(__uuidof(EAGetMailObjLib::MailClient))
        oClient->LicenseCode = _T("TryIt");

        oClient->Connect( oServer );
        _tprintf(_T("Connected\r\n"));

        _variant_t infos = oClient->GetMailInfos();
        SAFEARRAY *psa = infos.parray;
        long LBound = 0, UBound = 0;
        SafeArrayGetLBound( psa, 1, &LBound );
        SafeArrayGetUBound( psa, 1, &UBound );

        INT count = UBound-LBound+1;
        _tprintf(_T("Total %d emails\r\n"), count );

        for( long i = LBound; i <= UBound; i++ )
        {
            _variant_t vtInfo;
            SafeArrayGetElement( psa, &i, &vtInfo );

            IMailInfoPtr pInfo;
            vtInfo.pdispVal->QueryInterface(__uuidof(IMailInfo), (void**)&pInfo);

            TCHAR szFile[MAX_PATH+1];
            memset( szFile, 0, sizeof(szFile));

            // Generate a random file name by current local datetime,
            // You can use your method to generate the filename if you do not like it
            SYSTEMTIME curtm;
            ::GetLocalTime( &curtm );
            ::wsprintf( szFile, _T("%s\\%04d%02d%02d%02d%02d%02d%03d%d.eml"),
                szMailBox,
                curtm.wYear,
                curtm.wMonth,
                curtm.wDay,
                curtm.wHour,
                curtm.wMinute,
                curtm.wSecond,
                curtm.wMilliseconds,
                i );

            // Receive email from Gmail IMAP server
            IMailPtr oMail = oClient->GetMail(pInfo);

            // Save email to local disk
            oMail->SaveAs( szFile, VARIANT_TRUE );

            // Mark email as deleted from Gmail IMAP server.
            oClient->Delete( pInfo );
        }

        // Delete method just mark the email as deleted,
        // Quit method purge the emails from server exactly.
        infos.Clear();
        oClient->Quit();
    }
    catch( _com_error &ep )
    {
        _tprintf( _T("Error: %s"), (const TCHAR*)ep.Description());
    }

    return 0;
}

Gmail IMAP OAUTH

The Gmail IMAP and SMTP servers have been extended to support authorization via the industry-standard OAuth 2.0 protocol. Using OAUTH protocol, user can do authentication by Gmail Web OAuth instead of inputting user and password directly in application. This way is more secure, but a little bit complex.

Using Gmail IMAP OAUTH

Next Section

At next section I will introduce how to download emails from Yahoo account.

Appendix

Comments

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