发信类 sendMail.cs
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.Net.Mail;

/**//// <summary>
/// sendMail 的摘要说明
/// </summary>
public class sendMail

...{
public sendMail()

...{
//
// TODO: 在此处添加构造函数逻辑
//
}

/**//// <summary>
/// 发送邮件
/// </summary>
/// <param name="from">发送人邮件地址</param>
/// <param name="to">接收人邮件地址</param>
/// <param name="subject">邮件主题</param>
/// <param name="isBodyHtml">是否是Html</param>
/// <param name="body">邮件体</param>
/// <param name="smtpHost">SMTP服务器地址,例如:smtp.163.com</param>
/// <param name="userName">用户名</param>
/// <param name="password">密码</param>
/// <returns>是否成功</returns>
public static bool Send(string from, string to, string subject, bool isBodyHtml, string body, string smtpHost, string userName, string password)

...{
string[] ts = to.Split(',');
bool isSuccess = true;
foreach (string t in ts)

...{
try

...{
MailMessage mm = new MailMessage();
mm.From = new MailAddress(from);

mm.To.Add(new MailAddress(t.Trim()));

mm.Subject = subject;
mm.IsBodyHtml = isBodyHtml;
mm.Body = body;

SmtpClient sc = new SmtpClient();
sc.Host = smtpHost;

sc.UseDefaultCredentials = true;//winform中不受影响,asp.net中,false表示不发送身份严正信息
//smtpClient.EnableSsl = true;//如果服务器不支持ssl则报,服务器不支持安全连接 错误
sc.Credentials = new System.Net.NetworkCredential(userName, password);
sc.DeliveryMethod = SmtpDeliveryMethod.Network;

sc.Send(mm);
}
catch

...{
isSuccess = false;
}
}
return isSuccess;
}
}

调用发信函数
if (sendMail.Send("ycyangcai@163.com", "ycyangcai@163.com", "subject", true, "body", "smtp.163.com", "yangcai", "yangcai"))

...{
Response.Write("ok");
}
else

...{
Response.Write("no");
}
本例的类下载地址: http://www.cnblogs.com/Files/yangcai/sendMail.rar