The SMTP server requires a secure connection or the client was not authenticated.

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C#

ASP.NET

The following error is occured in my code.I want to send mail through smtp service via gmail. :

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. g14sm3507891wfh.10.


Code written by:

emailid = table.Rows[0]["EmailId"].ToString();
					MailMessage mail = new MailMessage();
					mail.To.Add(emailid);
					mail.From = new MailAddress(txtemail.Text.ToString());
					mail.Subject = "Registration";
					string Body = "Please Approve my Registration";
					mail.Body = Body;
					SmtpClient smtp = new SmtpClient("127.0.0.1");
					smtp.Host = "smtp.gmail.com";
					try
					{
						smtp.Send(mail);
						Response.Write("Mail sent successfully");
						clearcontrol();
					}
					catch (Exception ex)
					{
						Response.Write("Mail send failed");
					}