I have integrated email in C# and mail is received in spam in gmail how can I resolve it .using go daddy

public static string sendemail(string To, string message, string subject)
{
    try
    {
        MailMessage mail = new MailMessage();
        var smtpM = new SmtpClient();
        smtpM.EnableSsl = false;

        smtpM.Port = 25;

        smtpM.Host = "host.net";
        smtpM.Credentials = new NetworkCredential("mygmail.com", "paasword");

        string to = string.Join(",", To);
        mail.Bcc.Add(to);
        //mail.CC.Add(new MailAddress(txtcc.Text));
        mail.From = new MailAddress("host.com", "my - SYSTEMS");

        string html = message;
        mail.Body = html;
        mail.Subject = subject;
        mail.IsBodyHtml = true;

        smtpM.Send(mail);

        return "successfully Mail Sent";
    }
    catch (Exception ex)
    {
        return ex.ToString();
    }
}