asp.net webform 发送电子邮件

<div>
<h2>
发送电子邮件演示
</h2>
<table cellpadding="0" cellspacing="0" border="0" style="font-family: 宋体, Arial, Helvetica, sans-serif;
font-size: 15px; width: 411px;">
<tr>
<td class="style5">
邮箱地址：
</td>
<td class="style6">
<asp:TextBox ID="tb_Email" runat="server" Width="269px"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style5">
抄送至：
</td>
<td class="style6">
<asp:TextBox ID="tb_cc" runat="server" Width="268px"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style5">
邮件主题：
</td>
<td class="style6">
<asp:TextBox ID="tb_Subject" runat="server" Width="268px"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style5">
邮件内容：
</td>
<td class="style6">
<asp:TextBox ID="tb_Body" runat="server" Height="63px" TextMode="MultiLine" Width="266px"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style5">
添加附件：
</td>
<td class="style6">
<asp:FileUpload ID="tb_Attachment" runat="server" Width="265px" />
</td>
</tr>
<tr>
<td align="right" colspan="2">
<asp:Button ID="btn_SendEmail" runat="server" Text="发送邮件"
onclick="btn_SendEmail_Click"/>
</td>
</tr>
</table>
</div>

后端代码：

protected void btn_SendEmail_Click(object sender, EventArgs e)
{
//声明一个Mail对象
MailMessage mymail = new MailMessage();
//发件人地址
//如是自己，在此输入自己的邮箱
mymail.From = new MailAddress("[email protected]");
//收件人地址
mymail.To.Add(new MailAddress(tb_Email.Text));
//邮件主题
mymail.Subject = tb_Subject.Text;
//邮件标题编码
mymail.SubjectEncoding = System.Text.Encoding.UTF8;
//发送邮件的内容
mymail.Body = tb_Body.Text;
//邮件内容编码
mymail.BodyEncoding = System.Text.Encoding.UTF8;
//添加附件
Attachment myfiles = new Attachment(tb_Attachment.PostedFile.FileName);
mymail.Attachments.Add(myfiles);
//抄送到其他邮箱
mymail.CC.Add(new MailAddress(tb_cc.Text));
//是否是HTML邮件
mymail.IsBodyHtml = true;
//邮件优先级
mymail.Priority = MailPriority.High;
//创建一个邮件服务器类
SmtpClient myclient = new SmtpClient();
myclient.Host = "SMTP.163.com";
//SMTP服务端口
myclient.Port = 25;
//验证登录
myclient.Credentials = new NetworkCredential("@@@@@@", "*****");//"@"输入有效的邮件名, "*"输入有效的密码
myclient.Send(mymail);
}