发送邮件程序，亲测

public partial class Test_Default5 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        
    }
    /// <summary> 
    /// 发送邮件 
    /// </summary> 
    /// <param name="address">接收人:Eamil地址</param> 
    /// <param name="subject">主题</param> 
    /// <param name="body">邮件内容</param> 
    /// <param name="attachment">附件</param> 
    /// <param name="isBodyHtml">邮件是Html格式</param> 
    /// <returns></returns> 
    public  bool Send(string address, string subject, string body, Attachment attachment, bool isBodyHtml)
    {
        try
        {
            MailMessage mail = new MailMessage();
            mail.From = new MailAddress("yexinw@163.com");
            mail.To.Clear();
            mail.To.Add(new MailAddress(address));
            mail.Body = body;
            mail.BodyEncoding = Encoding.UTF8;
            mail.SubjectEncoding = Encoding.UTF8;
            mail.Subject = subject;
            mail.IsBodyHtml = isBodyHtml;
            mail.Priority = System.Net.Mail.MailPriority.Normal;
            if (attachment != null) mail.Attachments.Add(attachment);
            SmtpClient smtp = new SmtpClient("smtp.163.com", 25);
            smtp.UseDefaultCredentials = true;
            smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
            smtp.Credentials = new System.Net.NetworkCredential("yexinw@163.com", "");
            smtp.Send(mail);
            return true;
        }
        catch
        {
            Response.Write("发送失败！");
            return false;
        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        Send("yexinw@qq.com", "Test", "<br/>测试邮件", null, true);
       
    }
}