C# 发送邮件

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


namespace SendEmailExam
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            txtContent.Text = "<h1>Hello</h1>";
            txtTo.Text = "xxx@163.com";
            txtSubject.Text = "Hello";
            txtCC.Text = "xxx@126.com;xxx@163.com";
        }


        private void btnSend_Click(object sender, EventArgs e)
        {
            SmtpClient sc = new SmtpClient();
            NetworkCredential cred = new NetworkCredential("admin", "admin");
            sc.Credentials = cred;
            sc.Host = "smtp.163.com";
            MailMessage mm = new MailMessage();
            mm.From = new MailAddress("xxx@163.com", "xxx");
            mm.Sender = new MailAddress("xxx@163.com","xxx");
            string[] tos = txtTo.Text.Split(';');
            foreach (string item in tos)
            {
                mm.To.Add(new MailAddress(item));
            }
            string[] ccs = txtCC.Text.Split(';');
            foreach (string item in ccs)
            {
                mm.CC.Add(new MailAddress(item));
            }
            mm.Subject = txtSubject.Text;
            mm.Body = txtContent.Text;
            mm.IsBodyHtml = true;
            mm.Priority = MailPriority.High;
            mm.Attachments.Add(new Attachment(txtAccessory.Text));
            sc.Send(mm);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Multiselect = false;
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                txtAccessory.Text = ofd.FileName;
            }
        }
    }
}