无法向Hotmail发送邮件

Question

我一直在努力解决这个问题。我有两个按钮。一个按钮是从 Gmail发送邮件到Gmail ，另一个按钮用于 Gmail到Hotmail 。
我可以从我的Gmail 帐户发送邮件到另一个Gmail帐户，但从我的Gmail帐户发送到Hotmail时出现问题。

  

..邮箱不可用服务器.....服务器响应5.7.3请求   行动中止;用户未经过身份验证

五天后我即将放弃。 我已经检查了SO上的相关主题

1. Send email via Hotmail to gmail
2. Sending mail using Gmail

请不要将其标记为副本。

private void gmailTogmail(object sender, EventArgs e)
{
    var mail = new MailMessage();
    var c = new MailAddressCollection { txtto.Text.Trim() };
    mail.From = new MailAddress(txtfrom.Text.ToLower().Trim());

    // mail.To.Add((c[0].Address));
    mail.To.Add(txtto.Text.ToLower());
    mail.Subject = "for hilk";
    mail.Body = "some heeeeeee";
    mail.IsBodyHtml = true;

    var smtp = new SmtpClient
    {
        Host = "smtp.gmail.com",
        Port = 587,
        Credentials = new NetworkCredential(txtfrom.Text.Trim(), txtpass.Text.Trim()),
        EnableSsl = true
    };

    smtp.Send(mail);
    MessageBox.Show("ok");
}

private void gmailToHotmail(object sender, EventArgs e)
{
     SmtpClient SmtpServer = new SmtpClient("smtp.live.com");
        var mail = new MailMessage();
        mail.From = new MailAddress("mymail@gmail.com");
        mail.To.Add("mailSento@hotmail.com");
        mail.Subject = "Your Sub";
        mail.IsBodyHtml = true;
        //string htmlBody;
        //htmlBody = "HTML code";
        //mail.Body = htmlBody;
        SmtpServer.Port = 587;
        SmtpServer.Timeout = 5000;
        SmtpServer.UseDefaultCredentials = false;
        SmtpServer.Credentials = new System.Net.NetworkCredential("mymail@gmail.com", "Pass");
        SmtpServer.EnableSsl = true;
        SmtpServer.Send(mail);
        MessageBox.Show("ok");
}