MailMessage mailMessage = new MailMessage();
mailMessage.To.Add(this.txtTo.Text);
mailMessage.From = new System.Net.Mail.MailAddress(this.txtFrom.Text);
mailMessage.Subject = this.txtTitle.Text;
mailMessage.Body = this.txtContent.Text;
mailMessage.IsBodyHtml = true;
mailMessage.BodyEncoding = System.Text.Encoding.UTF8;
mailMessage.Priority = System.Net.Mail.MailPriority.Normal;

SmtpClient smtpClient = new SmtpClient();
smtpClient.Credentials = new System.Net.NetworkCredential(mailMessage.From.Address, this.txtPassword.Text);
smtpClient.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
smtpClient.Host = "smtp." + mailMessage.From.Host;
smtpClient.Port = 25;
smtpClient.Timeout = 3000;
smtpClient.EnableSsl = false;
smtpClient.Send(mailMessage);