SmtpClient sending without authentication

Question

I am sending emails to our clients from Java. And there is no any authentication for our SMTP. So I use the following code in Java to send it without authentication:

Properties props = new Properties();
Session session;
props.put("mail.smtp.auth", "false");
session = Session.getInstance(props, null);

This code works fine for sending emails from Java. But I want to send emails using ASP.NET and C#. But I am unable to send it. For sending it using C# I am using the following code:

SmtpClient smtp = new SmtpClient();
smtp.Host = "<My smtp.Host>";
smtp.EnableSsl = false;
smtp.Credentials = CredentialCache.DefaultNetworkCredentials;
smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
smtp.Send(message);

But it gives me the following error:

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Relaying not allowed: <Here email address of To>

How to send it without authentication?

score 29 · Accepted Answer · answered Jul 30 '12 at 10:24

29

From Msdn. If the UseDefaultCredentials property is set to false and the Credentials property has not been set, then mail is sent to the server anonymously.

answered Jul 30 '12 at 10:24

David Anderson

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I don't get it. Which property should I set to send it without authentication? – Himanshu Jul 30 '12 at 10:34
You remove `smtp.Credentials = ...` completely, and set `UseDefaultCredentials` to false. – David Anderson Jul 30 '12 at 10:37
2

Then your server disallows relaying, which means only the local server can send mail, or only a known user. – David Anderson Jul 30 '12 at 10:55

SmtpClient sending without authentication

1 Answers1