Please refer this code
HTML
<%@ Register TagPrefix="cc1" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<!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></title>
<style type="text/css">
body
{
font-family: Arial;
font-size: 10pt;
}
.table
{
border: 1px solid #ccc;
}
.table th
{
background-color: #F7F7F7;
color: #333;
font-weight: bold;
}
.table th, table td
{
padding: 5px;
border-color: #ccc;
}
.modalBackground
{
background-color: Black;
filter: alpha(opacity=60);
opacity: 0.6;
}
.modalPopup
{
background-color: #FFFFFF;
width: 350px;
border: 3px solid #0DA9D0;
border-radius: 12px;
padding: 0;
}
</style>
<asp:ContentPlaceHolder ID="head" runat="server">
</asp:ContentPlaceHolder>
</head>
<body>
<form id="form1" runat="server">
<cc1:ToolkitScriptManager runat="server">
</cc1:ToolkitScriptManager>
<div>
<table border="0" class="table" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td colspan="3" align="center">
<a href="Home.aspx">Home</a> | <a href="AboutUs.aspx">About Us</a>
<asp:LinkButton ID="btnShow" Text="Contact Us" runat="server" />
<hr />
</td>
</tr>
<tr>
<td style="width: 10%; border-right: 1px solid #000;">
Advertisements
</td>
<td style="width: 70%; overflow: auto;">
<asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
</asp:ContentPlaceHolder>
</td>
<td style="width: 10%; border-left: 1px solid #000;">
Advertisements
</td>
</tr>
</table>
</div>
<cc1:ModalPopupExtender ID="mp1" runat="server" PopupControlID="Panel1" TargetControlID="btnShow"
CancelControlID="btnClose" BackgroundCssClass="modalBackground">
</cc1:ModalPopupExtender>
<asp:Panel ID="Panel1" runat="server" Style="display: none" CssClass="modalPopup">
<table border="0">
<tr>
<td>
<asp:Label ID="Label1" runat="server" Text="Name*"></asp:Label><br />
</td>
<td>
<asp:TextBox ID="txtName" runat="server" ValidationGroup="contact"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="*"
ControlToValidate="txtName"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label2" runat="server" Text="Subject*"></asp:Label><br />
</td>
<td>
<asp:TextBox ID="txtSubject" runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ErrorMessage="*"
ControlToValidate="txtSubject"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label3" runat="server" Text="Email*"></asp:Label><br />
</td>
<td>
<asp:TextBox ID="txtEmail" runat="server"></asp:TextBox><br />
<asp:RegularExpressionValidator ID="valRegEx" runat="server" ControlToValidate="txtEmail"
ValidationExpression=".*@.*\..*" ErrorMessage="*Invalid Email address." Display="dynamic">
</asp:RegularExpressionValidator>
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ErrorMessage="*"
ControlToValidate="txtEmail"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td valign="top">
<asp:Label ID="Label4" runat="server" Text="Body*"></asp:Label>
</td>
<td>
<asp:TextBox ID="txtBody" runat="server" TextMode="MultiLine"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ErrorMessage="*"
ControlToValidate="txtBody"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
</td>
<td>
<asp:Button ID="btnSend" runat="server" Text="Send" OnClick="btnSend_Click" />
<asp:Button ID="btnClose" Text="Close" runat="server" />
</td>
</tr>
<tr>
<td>
</td>
<td>
<asp:Label ID="lblMessage" runat="server" Text="" ForeColor="Green"></asp:Label>
</td>
</tr>
</table>
</asp:Panel>
</form>
</body>
</html>
Add this in master page
Namespace
using System.Net;
using System.Net.Mail;
C#
protected void btnSend_Click(object sender, EventArgs e)
{
MailMessage mm = new MailMessage("sender@gmail.com", "receiver@gmail.com");
mm.Subject = txtSubject.Text;
mm.Body = "Name: " + txtName.Text + "<br /><br />Email: " + txtEmail.Text + "<br />" + txtBody.Text;
mm.IsBodyHtml = false;
SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com";
smtp.EnableSsl = true;
System.Net.NetworkCredential NetworkCred = new System.Net.NetworkCredential();
NetworkCred.UserName = "sender@gmail.com";
NetworkCred.Password = "xxxxx";
smtp.UseDefaultCredentials = true;
smtp.Credentials = NetworkCred;
smtp.Port = 587;
smtp.Send(mm);
lblMessage.Text = "Email Sent SucessFully.";
}
Screenshot
