C# yandex mail send error 5.5.4 Error: send AUTH command first

Question

I try to send mail using C# and yandex, but I get an error:

Error 5.5.4 Error: send AUTH command first

Here is my code. I try w

Answer 1

You must set sc.Credentials = new System.Net.NetworkCredential() after calling sc.UseDefaultCredentials = false;

UseDefaultCredentials = false will reset Credentials to null

try to switch lines order to:

sc.UseDefaultCredentials = false;
sc.Credentials = new System.Net.NetworkCredential(System.Configuration.ConfigurationManager.AppSettings["Email"].ToString(), 
                                                  System.Configuration.ConfigurationManager.AppSettings["Sifre"].ToString());

also valid settings for smtp.yandex.ru:

    smtpUserName=""
    enableSsl="true"
    smtpPassword=""
    smtpAuthentication="Basic"
    smtpServer="smtp.yandex.ru"
    smtpPort="465"