C# SmtpClient class not able to send email using gmail

Question

I'm having trouble sending email using my gmail account. I'm pulling my hair out. The same settings work fine in Thunderbird. Here's the code. I've also tried port 465 with no luck. ``` SmtpClient ss = new SmtpClient("smtp.gmail.com", 587); ss.Credentials = new NetworkCredential("username", "pass"); ss.EnableSsl = true; ss.Timeout = 10000; ss.DeliveryMethod = SmtpDeliveryMethod.Network; ss.UseDefaultCredentials = false; MailMessage mm = new MailMessage("donotreply@example.com", "destination@example.com", "subject here", "my body"); mm.BodyEncoding = UTF8Encoding.UTF8; mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure; ss.Send(mm); ``` Heres the error The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at Here's the stack trace ``` at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net.Mail.MailCommand.Send(SmtpConnection…

Accepted Answer

You won't believe what fixed my problem.

The Credentials property

```
ss.Credentials = new NetworkCredential("username", "pass");
```

must be declared after

```
ss.UseDefaultCredentials = false;
```

So the final working code listing is

```
SmtpClient ss = new SmtpClient("smtp.gmail.com", 587);
ss.EnableSsl = true;
ss.Timeout = 10000;
ss.DeliveryMethod = SmtpDeliveryMethod.Network;
ss.UseDefaultCredentials = false;
ss.Credentials = new NetworkCredential("username", "pass");

MailMessage mm = new MailMessage("donotreply@example.com", "destination@example.com", "subject here", "my body");
mm.BodyEncoding = UTF8Encoding.UTF8;
mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
ss.Send(mm);
```

Is this a bug?

C# SmtpClient class not able to send email using gmail

Solution

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