实现步骤：
1 创建一个对话框程序，把MailMessage.h/MailMessage.cpp和SMTP.h/SMTP.cpp加入到工程中。
2 添加如图所示得一些控件
IDC_COMBO_SERVER
IDC_COMBO_FROM
IDC_COMBO_TO
IDC_COMBO_SUBJECT
IDC_EDIT_BODY
IDSEND
3 为各个组合框控件添加变量
CComboBox m_ctrlComboTo;
CComboBox m_ctrlComboSubject;
CComboBox m_ctrlComboServer;
CComboBox m_ctrlComboFrom;
CString m_strComboFrom;
CString m_strComboServer;
CString m_strComboSubject;
CString m_strComboTo;
CString m_strEditBody;
并在构造函数中初始化
m_strComboFrom = _T("");
m_strComboServer = _T("");
m_strComboSubject = _T("");
m_strComboTo = _T("");
m_strEditBody = _T("");
4 在SMTPEMailDlg.h中加入
#include "MailMessage.h"
#include "SMTP.H"
再在CSMTPEMailDlg::OnInitDialog()中加入：
m_ctrlComboServer.InsertString(0,"mail.czvc.com");
m_ctrlComboServer.InsertString(1,"smtp.sina.com.cn");
m_ctrlComboServer.InsertString(2,"smtp.163.com");
m_ctrlComboServer.InsertString(3,"smtp.sohu.com");
m_ctrlComboServer.InsertString(4,"smtp.163.net");
m_ctrlComboServer.InsertString(5,"smtp.263.net
