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Problem :

I want to send mails using my web application. But my below code is showing me the below error:

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

5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM.

Below is my Code:

protected void mybtnsubmit_Click(object mysender, EventArgs e)
Ticket_MailTableAdapters.tbl_TicketTableAdapter tc; 
mytc = new Ticket_MailTableAdapters.tbl_TicketTableAdapter();
   DataTable mydt = new DataTable();
   mydt = mytc.GetEmail(dpl_cate.SelectedValue);
   foreach (DataRow row in mydt.Rows)
    string myeml = (row["Emp_Email"].ToString());
    var myfromAddress = "emailAddress";
    var mytoAddress = myeml;
    const string myfromPassword = "*****";
    string mybody = "Welcome..";
 // smtp settings
    var mysmtp = new MySystem.Net.Mail.SmtpClient();
         mysmtp.Host = "smtp.office365.com";
         mysmtp.Port = 587;
         mysmtp.EnableSsl = true;
         mysmtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
         mysmtp.Credentials = new NetworkCredential(myfromAddress, myfromPassword);
         mysmtp.UseDefaultCredentials = false;
         mysmtp.Timeout = 600000;
  // Passing values to smtp object
     mysmtp.Send(myfromAddress, mytoAddress, mysubject, mybody);


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1 Answer

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Solution :

In case you have not found the solution yet, then follow below things that to solve the same issue.

1.  Please make sure that NetworkCredentials you are setting must be correct. For example in my case since it was the office SMTP, user id must be used in the NetworkCredential along with domain name and not the actual email id.

2.  Also you need to set the "UseDefaultCredentials" to false first and after that set Credentials. If you try to set "UseDefaultCredentials" after that it will reset the NetworkCredential to null.

Hope it will solve your issue.

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