5.7.57 SMTP - Client was not authenticated to send anonymous mail during MAIL FROM error

Question

I have to send mails using my web application. Given the below code showing 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.

Help me to find a proper solution. Thank you.

Code:

protected void btnsubmit_Click(object sender, EventArgs e)
 {

   Ticket_MailTableAdapters.tbl_TicketTableAdapter tc;
   tc = new Ticket_MailTableAdapters.tbl_TicketTableAdapter();
   DataTable dt = new DataTable();
   dt = tc.GetEmail(dpl_cate.SelectedValue);
   foreach (DataRow row in dt.Rows)
    {
    string eml = (row["Emp_Email"].ToString());
    var fromAddress = "emailAddress";
    var toAddress = eml;
    const string fromPassword = "*****";
    string body = "Welcome..";
 // smtp settings
    var smtp = new System.Net.Mail.SmtpClient();
       {
         smtp.Host = "smtp.office365.com";
         smtp.Port = 587;
         smtp.EnableSsl = true;

         smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
         smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
         smtp.UseDefaultCredentials = false;
         smtp.Timeout = 600000;
       }
  // Passing values to smtp object
     smtp.Send(fromAddress, toAddress, subject, body);
     }
  } 
 }

Solution 1

You seem to be passing the From address as emailAddress, which is not a proper email address. For Office365 the From needs to be a real address on the Office365 system.

You can validate that if you hardcode your email address as the From and your Office 365 password.

Don't leave it there though of course.

Solution 2

@Reshma- In case you have not figured it yet, here are below things that I tried and it solved the same issue.

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

2. You need to set "UseDefaultCredentials" to false first and then set Credentials. If you set "UseDefaultCredentials" after that it resets the NetworkCredential to null.

Hope it helps.

Solution 3

I spent way too much time on this and the solution was super simple. I had to use my "MX" as the host and port 25.

        var sClient = new SmtpClient("domain-com.mail.protection.outlook.com");
        var message = new MailMessage();

        sClient.Port = 25;
        sClient.EnableSsl = true;
        sClient.Credentials = new NetworkCredential("user", "password");
        sClient.UseDefaultCredentials = false;

        message.Body = "Test";
        message.From = new MailAddress("[email protected]");
        message.Subject = "Test";
        message.CC.Add(new MailAddress("[email protected]"));

        sClient.Send(message);

Solution 4

I use to have the same problem.

Add the domain solved it..

mySmtpClient.Credentials = New System.Net.NetworkCredential("[email protected]", "password", "domain.com")

Solution 5

In my case, 2 Factor Authentication was turned on for the FROM account in Office 365. Once that was turned off, the email sent successfully.

View more solutions

Comments

[Mahesh Kava]

why not increase the Timeout?

[fk2]

Did you anonymize this, or are you actually trying to send over office.com with that login?

[Rishi Jagati]

@reshma, What changes did you make? Facing the same issue.

[Raphael]

I've been ableto send an email with the SMTP config shown, but I moved smtp.UseDefaultCredentials = false; before smtp.Credentials = ... as Kiquenet write below

[nwestfall]

That's it! I didn't know "UseDefaultCredentials" clears the Credentials. Thanks!

[EJA]

This is the correct solution for me. I've had an application running, sending daily emails for over a year, suddenly it stopped working. The change to fix it is this one, even though my network credentials aren't actually my email, this fix worked.

[wajira000]

This one is worked for me. check this Microsoft article support.office.com/en-us/article/…

[Simon Price]

This worked for me, but I had to then go to sender.office.com to delist my IP address

[Muhammad Ali]

for me sClient.EnableSsl = true; was not defined.

[Kevin .NET]

I changed only one time. It told me the password expired when I try to login.

[devlin carnate]

what language is this? It doesn't appear to be C# SmtpClient()

[Justinas Jakavonis]

It's properties list which can be parsed in any language.

[Kiquenet]

You need to set "UseDefaultCredentials" to false first and then set Credentials. If you set "UseDefaultCredentials" after that it resets the NetworkCredential to null.

[Kiquenet]

How TLS enable in C# ?

[Kiquenet]

How you get the MX value ?

[Kiquenet]

Which is the difference about domain-com.mail.protection.outlook.com and smtp.office365.com ? Can I send to xxx@anotherDomain recipients ?

[Weihui Guo]

In my case, it doesn't matter which one goes first. As long as the "UseDefaultCredentials" is false. It works. I wonder why.

[Weihui Guo]

It's not adding the domain name, but using the email address as the userName solved my problem. NetworkCredential(email, password);

[Lez]

Using the MX record as host enables you to send email only to internal email addresses (ie only to the same domain as the sending address)

[Abdus Salam Azad]

This is not like C# SmtpClient()

[Martijn]

@Kiquenet You may need to ask your system administrator. More info here: docs.microsoft.com/en-us/exchange/mail-flow-best-practices/…

[Kiquenet]

How is 2 Factor Authentication ?

[West]

Finally a working answer for me. Thanks! I was using a simple string for the To field instead of type MailAddress. The error message is definitely misleading

[Chirag]

Step 1 worked for me. I had Authenticated SMTP unchecked. When checked and saved, emails started working through my CSharp program.