System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authentication Required. inD:\FINALPROJECT\DADC\DADS_orginial_live\Registration\frmRegistration.aspx.cs:line 725 at Registration.frmRegistration.btnEmailOTP_Click(Object sender, EventArgs e) in D:\FINALPROJECT\DADC\DADS_orginial_live\Registration\frmRegistration.aspx.cs:line 677