C++发邮件用的是阻塞式socket模型，发送完数据后需要接收返回值，才能接着发送。
本程序不发送邮件附件，发附件的实例：C++实现含附件的邮件发送功能
#include <iostream>
#include <string>
#include <WinSock2.h> //适用平台 Windows
using namespace std;
#pragma comment(lib, "ws2_32.lib") /*链接ws2_32.lib动态链接库*/
int main()
{
char buff[500]; //recv函数返回的结果
string message;
WSADATA wsaData;
WORD wVersionRequested = MAKEWORD(2, 1);
//WSAStarup，即WSA(Windows SocKNDs Asynchronous，Windows套接字异步)的启动命令
int err = WSAStartup(wVersionRequested, &wsaData);
cout << "WSAStartup:" << err << endl;
SOCKET sockClient; //客户端的套接字
sockClient = socket(AF_INET, SOCK_STREAM, 0); //建立socket对象
HOSTENT* pHostent;
pHostent = gethostbyname("smtp.126.com"); //得到有关于域名的信息
SOCKADDR_IN addrServer; //服务端地址
addrServer.sin_addr.S_un.S_addr = *((DWORD *)pHostent->h_addr_list[0]); //得到smtp服务器的网络字节序的ip地址
addrServer.sin_family = AF_INET;
addrServer.sin_port = htons(25); //连接端口25
//int connect (SOCKET s , const struct sockaddr FAR *name , int namelen ); //函数原型
err = connect(sockClient, (SOCKADDR*)&addrServer, sizeof(SOCKADDR)); //向服务器发送请求
cout << "connect:" << err << endl;
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "connect:" << buff << endl;
/*
登录邮件服务器
*/
message = "ehlo 126.comrn";
send(sockClient, message.c_str(), message.length(), 0); //发送ehlo命令
buff[recv(sockClient, buff, 500, 0)] = ' '; //接收返回值
cout << "helo:" << buff << endl; //输出返回值
message = "auth login rn";
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "auth login:" << buff << endl;
/*
发送base64加密的用户名、密码
*/
message = "xxxxrn"; //base64 编码的用户名
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "usrname:" << buff << endl;
message = "xxxxrn";//base64 编码的密码
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "password:" << buff << endl;
/*
使用 MAIL 命令指定发送者
使用 RCPT 命令指定接收者，可以重复使用RCPT指定多个接收者
*/
message = "MAIL FROM:<xxxx@126.com> rnRCPT TO:<xxxx@126.com> rn";
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "mail from: " << buff << endl;
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "rcpt to: " << buff << endl;
/*
使用 DATA 命令告诉服务器要发送邮件内容
*/
message = "DATArn";
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "data: " << buff << endl;
message = "From: Bob@example.comrn
To: Alice@example.comrn
Cc: theboss@example.comrn
subject: subjectrnrn
Hello Alicern
This is a test message with 4 header fields and 4 lines in the message bodyrn
your friendrn
Bobrn.rn"; //注意subject关键字与正文之间要有一个空行
send(sockClient, message.c_str(), message.length(), 0);
message = "QUITrn";
send(sockClient, message.c_str(), message.length(), 0);
buff[recv(sockClient, buff, 500, 0)] = ' ';
cout << "QUIT:" << buff << endl;
system("pause");
}
