Question

I know this has been disscused a lot, but I I’m not asking how to do it, I’m just asking why it doesn’t work. What I am doing wrong. It says that the email was sent succesfully but I don’t see it in my inbox. I want to send an email to a gmail account, not through it.

#include <iostream>
#include <windows.h>
#include <fstream>
#include <conio.h>
#pragma comment(lib, "ws2_32.lib")

// Insist on at least Winsock v1.1
const int VERSION_MAJOR = 1;
const int VERSION_MINOR = 1;

#define CRLF "\r\n"                 // carriage-return/line feed pair
using namespace std;

// Basic error checking for send() and recv() functions
void Check(int iStatus, char *szFunction)
{
  if((iStatus != SOCKET_ERROR) && (iStatus))
    return;

  cerr<< "Error during call to " << szFunction << ": " << iStatus << " - " << GetLastError() << endl;
}

int main(int argc, char *argv[])
{
  int         iProtocolPort        = 25;
  char        szSmtpServerName[64] = "";
  char        szToAddr[64]         = "";
  char        szFromAddr[64]       = "";
  char        szBuffer[4096]       = "";
  char        szLine[255]          = "";
  char        szMsgLine[255]       = "";
  SOCKET      hServer;
  WSADATA     WSData;
  LPHOSTENT   lpHostEntry;
  LPSERVENT   lpServEntry;
  SOCKADDR_IN SockAddr;

  // Check for four command-line args
  //if(argc != 5)
   // ShowUsage();

  // Load command-line args
  lstrcpy(szSmtpServerName, "smtp.gmail.com");
  lstrcpy(szToAddr, "[e-mail]");
  lstrcpy(szFromAddr, "[e-mail]");

  // Create input stream for reading email message file
  ifstream MsgFile("D:\\d.txt");

  // Attempt to intialize WinSock (1.1 or later)
  if(WSAStartup(MAKEWORD(VERSION_MAJOR, VERSION_MINOR), &WSData))
  {
    cout << "Cannot find Winsock v" << VERSION_MAJOR << "." << VERSION_MINOR << " or later!" << endl;

    return 1;
  }

  // Lookup email server's IP address.
  lpHostEntry = gethostbyname(szSmtpServerName);
  if(!lpHostEntry)
  {
    cout << "Cannot find SMTP mail server " << szSmtpServerName << endl;

    return 1;
  }

  // Create a TCP/IP socket, no specific protocol
  hServer = socket(PF_INET, SOCK_STREAM, 0);
  if(hServer == INVALID_SOCKET)
  {
    cout << "Cannot open mail server socket" << endl;

    return 1;
  }

  // Get the mail service port
  lpServEntry = getservbyname("mail", 0);

  // Use the SMTP default port if no other port is specified
  if(!lpServEntry)
    iProtocolPort = htons(IPPORT_SMTP);
  else
    iProtocolPort = lpServEntry->s_port;

  // Setup a Socket Address structure
  SockAddr.sin_family = AF_INET;
  SockAddr.sin_port   = iProtocolPort;
  SockAddr.sin_addr   = *((LPIN_ADDR)*lpHostEntry->h_addr_list);

  // Connect the Socket
  if(connect(hServer, (PSOCKADDR) &SockAddr, sizeof(SockAddr)))
  {
    cout << "Error connecting to Server socket" << endl;

    return 1;
  }

  // Receive initial response from SMTP server
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() Reply");

  // Send HELO server.com
  sprintf(szMsgLine, "HELO %s%s", szSmtpServerName, CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() HELO");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() HELO");

  // Send MAIL FROM: <[e-mail]>
  sprintf(szMsgLine, "MAIL FROM:<%s>%s", szFromAddr, CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() MAIL FROM");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() MAIL FROM");

  // Send RCPT TO: <[e-mail]>
  sprintf(szMsgLine, "RCPT TO:<%s>%s", szToAddr, CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() RCPT TO");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() RCPT TO");

  // Send DATA
  sprintf(szMsgLine, "DATA%s", CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() DATA");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() DATA");
  //strat writing about the subject, end it with two CRLF chars and after that you can 
  //write data to the body oif the message
  sprintf(szMsgLine, "Subject: My own subject %s%s", CRLF, CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() DATA");




  // Send all lines of message body (using supplied text file)
  MsgFile.getline(szLine, sizeof(szLine));             // Get first line

  do         // for each line of message text...
  {
    sprintf(szMsgLine, "%s%s", szLine, CRLF);
    Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() message-line");
    MsgFile.getline(szLine, sizeof(szLine)); // get next line.
  } while(!MsgFile.eof());

  // Send blank line and a period
  sprintf(szMsgLine, "%s.%s", CRLF, CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() end-message");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() end-message");

  // Send QUIT
  sprintf(szMsgLine, "QUIT%s", CRLF);
  Check(send(hServer, szMsgLine, strlen(szMsgLine), 0), "send() QUIT");
  Check(recv(hServer, szBuffer, sizeof(szBuffer), 0), "recv() QUIT");

  // Report message has been sent
  cout<< "Sent " << argv[4] << " as email message to " << szToAddr << endl;

  // Close server socket and prepare to exit.
  closesocket(hServer);

  WSACleanup();
  _getch();
  return 0;
}

Answer 1

Google Mail SMTP server will not accept any mail without authentication. You could possibly succeed if sender was non-GMail user and you could make the session look like relayed delivery from another mail server into mailbox of GMail user, but as soon as your sender is @gmail.com this option is not available.

You have to do authentication, which is SSL or TLS enabled session (ports 465, 587), and then password authentication. This way the mail server will accept your delivery. You can use SChannel API to do TLS/SSL for you.

Now when you have this code snippet, you need to look at the response sent to you. I am sure you have something that explains that authentication is mandatory.