How to sen emails from to others account

protected void SendMail()
   {
       // Gmail Address from where you send the mail
       var fromAddress = "rajeshkumar.pani@gmail.com";
       // any address where the email will be sending
       var toAddress = "dsssweta@gmail.com";
       //Password of your gmail address
       const string fromPassword = "1234";
       // Passing the values and make a email formate to display
       string subject = "Hi";
       string body = "From: ";
      
       // smtp settings
       var smtp = new System.Net.Mail.SmtpClient();
       {
           smtp.Host = "localhost";
           smtp.Port = 25;
           smtp.EnableSsl = true;
           smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
           smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
          // smtp.Timeout = 20000;
       }
       // Passing values to smtp object
       smtp.Send(fromAddress, toAddress, subject, body);
   }