Email error while sending mail from C# code

Question

I am getting the following error

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

How to resolve this? My code:

MailMessage mail = new MailMessage();
mail.From = new MailAddress(FromAddress);
mail.To.Add(email);
mail.Subject = "Forgot Password";
mail.Body = SendMessage;
mail.IsBodyHtml = true;
SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");
SmtpServer.Port = 587;
SmtpServer.DeliveryMethod = SmtpDeliveryMethod.Network;
NetworkCredential myCreds = new NetworkCredential(EmailUsername, EmailPassword);
SmtpServer.Credentials = myCreds;
SmtpServer.EnableSsl = true;
SmtpServer.UseDefaultCredentials = true;
SmtpServer.Send(mail);

Webconfig as follows

<add key="FromAddress" value="[email protected]"/>
<add key="EmailUsername" value="[email protected]"/>
<add key="EmailPassword" value="Josco@321"/>

Changed my email settings as follows.

FromAddress and EmailUsername are same email.

Not directly relevant to your question, but MailMessage and SmtpClient both implement IDisposable, and in case of SmtpClient in particular, you can actually exhaust resources if you don't dispose. — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Aug 8, 2017 at 18:56
Be sure to change your password as it is showing in the question ;-) — IrishChieftain
– IrishChieftain, Commented Aug 8, 2017 at 19:05

IrishChieftain · Accepted Answer · 2017-08-13 04:30:32Z

4

Ensure you set SmtpClient.Credentials AFTER calling SmtpClient.UseDefaultCredentials = false.

The order is important as setting SmtpClient.UseDefaultCredentials = false will reset SmtpClient.Credentials to null.

edited Aug 13, 2017 at 4:30

answered Aug 8, 2017 at 18:51

IrishChieftain

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