private void SendEmail()
{
        MailMessage mailmessage = new MailMessage();
        mailmessage.From = new MailAddress("[email protected]");//发件人
        mailmessage.To.Add(new MailAddress("[email protected]"));//收件人
        mailmessage.To.Add(new MailAddress("[email protected]"));//收件人
        mailmessage.Subject = "进销存系统";//邮件主题
        mailmessage.Body = “内容：<br />"+richTextBox1.Text.Trim();//邮件正文内容
        mailmessage.IsBodyHtml = true;//邮件正文内容格式是否为HTML格式
        SmtpClient sClient = new SmtpClient();
        sClient.Host = "smtp.sina.com.cn";//发件人邮箱的smtp服务器
        sClient.Credentials = new NetworkCredential("[email protected]", "mima");//发件人登陆该smtp服务器需要的账号，密码
        try
        {
            sClient.Send(mailmessage);//开始发送Email
            MessageBoxEx.Show("发送成功！");
        }
        catch (Exception e)
        {
            MessageBoxEx.Show("发送失败！\n"+e.Message);
        }
}