Here in this blog I am trying to explain you about sending emails in

ASP.NET by using namespace System.Web.Mail.

using System.Web.Mail; 
try 
            { 
                string smtpServer = "relay-hosting.secureserver.net"; 
                string userName = "contact@yourdomain.com"; 
                int cdoBasic = 1; 
                int cdoSendUsingPort = 2; 
                MailMessage msg = new MailMessage(); 
                if (userName.Length > 0) 
                { 
                    msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserver", smtpServer); 
                    msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserverport", 25); 
                    msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusing", cdoSendUsingPort); 
                    msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", cdoBasic); 
                    //msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", userName); 
                    // msg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", password); 
                } 
                msg.To = "contact@yourdomain.com"; 
                msg.From = "contact@yourdomain.com"; 
                msg.BodyFormat = MailFormat.Html; 
                msg.Subject = txtSubject.Text;           
                msg.Body = "Name: " + txtName.Text + "<br /><br />Company: " + txtCompany.Text + "<br /><br />Email: " + txtEmail.Text + "<br />" + txtDetails.Text; 
                SmtpMail.SmtpServer = smtpServer; 
                SmtpMail.Send(msg); 
 
                msg.To = txtEmail.Text.Trim(); 
                msg.From = "donotreply@yourdomain.com"; 
                msg.BodyFormat = MailFormat.Html; 
                msg.Subject = txtSubject.Text; 
                msg.Body = @"Hi,<br/> 
                Thanks for contacting , we will review your information and try to get back to you ASAP.<br/> 
                Thanks; 
 
                SmtpMail.SmtpServer = smtpServer; 
                SmtpMail.Send(msg); 
                ValidationSummary1.Visible = false; 
                lblStatus.Visible = true; 
                lblStatus.Text = "Message Sent Sucessfully."; 
 
            } 
            catch 
            { 
 
            }