SMTP Email not going from Asp.net C# Project

Hi,

I am trying to send email from Asp.net Project. I have tried all available options but no success.

I have already changed SMTP = Authentication true in Exchange.

ERROR : "Failure Sending Email"

Below is code, I am using

try

            {

                MailMessage Msg = new MailMessage();

                // Sender e-mail address.

                Msg.From = new MailAddress("******@gxxxxxoin.com"); <Modified by moderator due to privacy>

                // Recipient e-mail address.

                Msg.To.Add(txtTo.Text);

                Msg.Subject = txtSubject.Text;

                Msg.Body = txtBody.Text;

                // your remote SMTP server IP.

                SmtpClient smtp = new SmtpClient();

                smtp.Host = "gxxxxxoin-com.mail.protection.outlook.com"; ----- Trying with MX Record

                //   smtp.Host = "smtp.office365.com"; -------- We have also tried with this setting.

                smtp.Port = 587;

                smtp.UseDefaultCredentials = false;

                smtp.Credentials = new System.Net.NetworkCredential(txtUsername.Text, txtpwd.Text);

                smtp.EnableSsl = true;

                smtp.Send(Msg);

                Msg = null;

                Label1.Text = "sucess";

                Page.RegisterStartupScript("UserMsg", "<script>alert('Mail sent thank you...');if(alert){ window.location='SendMail.aspx';}</script>");

            }

            catch (Exception ex)

            {

                Label1.Text = ex.Message;

            }