Send Email programmatically using your Gmail account

protected void btnSendEmail_Click(object sender, EventArgs e)
{
   // Create Mail Message Object with content that you want to send with mail.
   System.Net.Mail.MailMessage MyMailMessage = new System.Net.Mail.MailMessage("dotnetguts@gmail.com","myfriend@yahoo.com",
"This is the mail subject", "Just wanted to say Hello");

   MyMailMessage.IsBodyHtml = false;

   // Proper Authentication Details need to be passed when sending email from gmail
   System.Net.NetworkCredential mailAuthentication = new
   System.Net.NetworkCredential("dotnetguts@gmail.com", "myPassword");

   // Smtp Mail server of Gmail is "smpt.gmail.com" and it uses port no. 587
   // For different server like yahoo this details changes and you can
   // Get it from respective server.
   System.Net.Mail.SmtpClient mailClient = new System.Net.Mail.SmtpClient("smtp.gmail.com",587);

   // Enable SSL
   mailClient.EnableSsl = true;

   mailClient.UseDefaultCredentials = false;

   mailClient.Credentials = mailAuthentication;

   mailClient.Send(MyMailMessage);
}