ASP.NET

<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" DataObjectTypeName="G1_OnlineStoreObjects.Book"
        DeleteMethod="Delete" SelectMethod="LoadBySeries" TypeName="G1_OnlineStoreDAO.BookDAO"
        UpdateMethod="Update">
        < SelectParameters >
            <asp:QueryStringParameter Name="seriesID" Type="Int32" QueryStringField="SeriesID" />
        < / SelectParameters >
    < / asp:ObjectDataSource >
    
    <asp:ObjectDataSource ID="ObjectDataSource2" runat="server" DataObjectTypeName="G1_OnlineStoreObjects.Book"
        DeleteMethod="Delete" SelectMethod="LoadByVolumes" TypeName="G1_OnlineStoreDAO.BookDAO"
        UpdateMethod="Update">
        < SelectParameters >
            <asp:QueryStringParameter Name="volumeID" Type="Int32" QueryStringField="VolumeID" />
        < / SelectParameters >
    < / asp:ObjectDataSource >

 <asp:GridView Visible="false" ID="GridView1" runat="server" AutoGenerateColumns="False"
        DataKeyNames="ID,SeriesID,VolumeID" DataSourceID="ObjectDataSource1" CellPadding="4"
        ForeColor="#333333" GridLines="None">
        < Columns >
            <asp:CommandField ShowEditButton="True" ShowDeleteButton="True" />
            <asp:BoundField DataField="BookName" HeaderText="BookName" SortExpression="BookName" />
        < / Columns >
< / asp:GridView >

 <asp:GridView Visible="false" ID="GridView2" runat="server" AutoGenerateColumns="False" DataKeyNames="ID,VolumeID,SeriesID"
        CellPadding="4" DataSourceID="ObjectDataSource2" ForeColor="#333333" GridLines="None">
        < Columns >
            <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" />
            <asp:BoundField DataField="BookName" HeaderText="BookName" SortExpression="BookName" />
        < / Columns >   
    < / asp:GridView >

Server Error in '/VICTORIAIN' Application.
Mailbox unavailable. The server response was: not local host hotmail.com, not a gateway
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: not local host hotmail.com, not a gateway

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SmtpFailedRecipientException: Mailbox unavailable. The server response was: not local host hotmail.com, not a gateway]
   System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) +858231
   System.Net.Mail.SmtpClient.Send(MailMessage message) +2004
   Contact_Us.send_data_to_mail() +189
   Contact_Us.BtnSubmit_Click(Object sender, EventArgs e) +18
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1746


Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433 

SmtpClient smtpClient = new SmtpClient();
MailMessage message = new MailMessage();

MailAddress fromAddress = new MailAddress(TxtEmail.Text, TxtName.Text);
message.From = fromAddress;
message.To.Add("rohanrajpoot@in.com");
message.Subject = "This person has contacted us!";
message.IsBodyHtml = false;
message.Body = TxtMessage.Text;
smtpClient.Send(message);

<system.net>
  <mailSettings>
    <smtp>
      <network host="myhostname" port="25" userName="loginname" password="pass" defaultCredentials="true" />
    </smtp>
  </mailSettings>
</system.net>