Web.config

<appSettings>

<add key=”SMTP” value=”smtp.gmail.com”/>

<add key=”FROMEMAIL” value=”Gmail UserName”/>

<add key=”FROMPWD” value=”GiveGmailPassword”/>

</appSettings>

give correct gmail username like  lokeshasp@gmail.com

give correct gmail password

Giving correct username and password of gmail. Gmail  SMTP server will assume is an authenticated user. For this authenticated details of gmail mails will sent to yahoo,gmail,etc..

using System.Net.Mail;

write below code in page load or button click

MailMessage mail = new MailMessage();

mail.To.Add(”lokeshdotnet09@yahoo.com”);

mail.From = new MailAddress(”lokeshasp@gmail.com”);

mail.Subject = “Test Email”;

string Body = “<b>Welcome to lotus.Com!!</b>”;

mail.Body = Body;

mail.IsBodyHtml = true;

SmtpClient smtp = new SmtpClient();

smtp.Host = ConfigurationManager.AppSettings["SMTP"];

smtp.Credentials = new System.Net.NetworkCredential(ConfigurationManager.AppSettings["FROMEMAIL"], ConfigurationManager.AppSettings["FROMPWD"]);

smtp.EnableSsl = true;

smtp.Send(mail);