发送E-mail的类，经测试，可以发送(推荐）

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;
using System.Net.Mail;
using System.Net;
using System.IO;

namespace KuaiCan.Web
{
    /// <summary>
    /// 发送E-mail的类，经测试，可以发送(推荐）
    /// </summary>
    public class SendMail
    {
        public string SendEmail(string toAddr, string title, string content)
        {
            MailMessage msg = new MailMessage();
            msg.To.Add(toAddr);
            msg.To.Add("xxxxxxxxxx@163.com");
            msg.CC.Add("xxxxxxxxxx@163.com");
            msg.From = new MailAddress("xxxxxxxxxx@163.com", "Automation Mercer", System.Text.Encoding.UTF8);
            msg.Subject = title;
            msg.SubjectEncoding = System.Text.Encoding.UTF8;
            msg.Body = content;
            msg.BodyEncoding = System.Text.Encoding.UTF8;
            msg.IsBodyHtml = false;
            msg.Priority = MailPriority.Normal;
            SmtpClient client = new SmtpClient();
            client.Credentials = new NetworkCredential("xxxxxxxxxx@163.com", "密码");
            client.Port = 25; //587, 465, 995
            client.Host = "smtp.163.com";
            //client.EnableSsl = true;
            //object userState = msg;
            try
            {
                client.Send(msg);
                return "sucess";
            }
            catch (SmtpException ex)
            {
                return ex.Message + "SendEmail error";
            }
        }

    }
}