using System.Net.Mail;
using System.IO;

                MailMessage mail = new MailMessage();
                SmtpClient SmtpServer = new SmtpClient(smtp);
                mail.From = new MailAddress("This is the mail from");
                mail.To.Add("[email protected]");
                mail.Subject = "Some subject";
                mail.IsBodyHtml = true; //If You want Html Body
                SmtpServer.Port = 25;
                SmtpServer.Credentials = new System.Net.NetworkCredential(user, pass);
                SmtpServer.EnableSsl = True; //if gmail use true
                SmtpServer.Send(mail);

mail.From = new MailAddress("mail");