用C#发送邮件

using System;
using System.Collections.Generic;
using System.Text;
using System.Web.Mail;
using System.IO;

namespace Mail
{
    public class Mail
    {
        string from;
      
        public string From
        {
            get { return from; }
            set { from = value; }
        }
        string to;

        public string To
        {
            get { return to; }
            set { to = value; }
        }
        string stmpServer;
        string password;
        string subject;

        public string Subject
        {
            get { return subject; }
            set { subject = value; }
        }
        string body;

        public string Body
        {
            get { return body; }
            set { body = value; }
        }

        string attachment;

        public string Attachment
        {
            get { return attachment; }
            set { attachment = value; }
        }
        static MailMessage mailMessage;
        public static void setMail(string from,string password,string stmpServer)
        {
            mailMessage = new MailMessage();
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1");
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", from);
            mailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", password);
            SmtpMail.SmtpServer = stmpServer;
        }
        public string Send()
        {
            if (from != null && from != "" && from.IndexOf("@") != -1)
                Mail.mailMessage.From = from;
            else
                return "无效的发件人邮件！";
            if (to != null && to != "" && to.IndexOf("@") != -1)
                Mail.mailMessage.To = to;
            else
                return "无效的收件人邮件！";
            if (subject != null)
                Mail.mailMessage.Subject = subject;
            else
                Mail.mailMessage.Subject = "无标题";
            if (body != null)
                Mail.mailMessage.Body = body;
            else
                Mail.mailMessage.Body = "";
            if (attachment != "" && attachment != null)
                Mail.mailMessage.Attachments.Add(new MailAttachment(attachment));

             Mail.mailMessage.BodyFormat = MailFormat.Html;
            try
            {
                SmtpMail.Send(mailMessage);
                return "邮件发送成功！";
            }
            catch (Exception ex)
            {
                return ex.Message;
                throw ex;
            }
        }
    }
}