一个邮箱的问题，急

提示发送失败，是不是缺少CS导致的。不太明白，麻烦大家给看看<%@ page language="C#" autoeventwireup="true" inherits="mail, App_Web_y7sjjnaf" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>邮箱</title>
<style type="text/css">
<!--
body {
background-color: #f6f9fd;
margin-left: 0px;
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
background-image: url(images/30295_top.jpg);
}
-->
            </style>
<link href="css/ldj.css" rel="stylesheet" type="text/css">
</head>
<body>
    <form id="form1" runat="server">
      <p>&nbsp;</p>
  <p>&nbsp;</p>
  <table width="60%" border="0" align="center" cellpadding="0" cellspacing="1" bgcolor="#b4e7e9">
              <tr>
                <td valign="top" bgcolor="#FFFFFF">
  <table width="100%" border="0" cellpadding="0" cellspacing="0" background="images/bt002.jpg">
                <tr>
                  <td height="25" align="center" class="blue"><p><strong>发 送 邮 件</strong></p>
                  </td>
                </tr>
              </table>
  </td>
          </tr>
              <tr>
                <td height="405" valign="middle" bgcolor="#FFFFFF">
                  <table width="99%" border="0" align="center" cellpadding="0" cellspacing="0" bgcolor="#b4e7e9" class="gray1">
              <tr>
                <td><table width="100%" border="0" cellspacing="1" cellpadding="5">
          <tr>
            <td align="right" bgcolor="#FFFFFF"><asp:Label ID="Label1" runat="server" Text="发送到"></asp:Label></td>
            <td bgcolor="#FFFFFF"><asp:DropDownList ID="ddltype" runat="server">
              <asp:ListItem Value="邮箱地址1">邮箱名称1</asp:ListItem>
              <asp:ListItem Value="邮箱地址2">邮箱名称2</asp:ListItem>
              <asp:ListItem Value="邮箱地址3">邮箱名称3</asp:ListItem>
            </asp:DropDownList></td>
          </tr>
          <tr>
            <td align="right" bgcolor="#FFFFFF"><asp:Label ID="Label2" runat="server" Text="标题"></asp:Label></td>
            <td bgcolor="#FFFFFF"><asp:TextBox ID="txttitle" runat="server"></asp:TextBox>
              <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txttitle"
            ErrorMessage="请填写邮件标题" validationgroup="mail"></asp:RequiredFieldValidator></td>
          </tr>
          <tr>
            <td align="right" bgcolor="#FFFFFF"><asp:Label ID="Label4" runat="server" Text="回复邮箱地址"></asp:Label></td>
            <td bgcolor="#FFFFFF"><asp:TextBox ID="txthuifu" runat="server"></asp:TextBox>
              <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="txthuifu"
            ErrorMessage="请正确填写回复邮箱地址" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"
            validationgroup="mail"></asp:RegularExpressionValidator>
              <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ControlToValidate="txthuifu"
            ErrorMessage="回复邮件地址不能为空" validationgroup="mail"></asp:RequiredFieldValidator></td>
          </tr>
          
          <tr>
            <td align="right" valign="top" bgcolor="#FFFFFF"><asp:Label ID="Label3" runat="server" Text="内容"></asp:Label></td>
            <td bgcolor="#FFFFFF"><asp:TextBox ID="txtcontent" runat="server" Height="239px" TextMode="MultiLine" Width="358px" OnTextChanged="txtcontent_TextChanged"></asp:TextBox>
              <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="txtcontent"
            ErrorMessage="请填写内容" validationgroup="mail"></asp:RequiredFieldValidator></td>
          </tr>
          <tr>
            <td align="right" bgcolor="#FFFFFF">&nbsp;</td>
            <td bgcolor="#FFFFFF"><asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="发 送" validationgroup="mail" /></td>
          </tr>
        </table>
        </td>
              </tr>
      </table>
        
    </td>
</tr>
  </table>    </form>
</body>
</html>