C#. SMTP The server response was: 5.7.0 Authentication Required

Question

Error: The SMTP server requires a secure connecton or the client was not authenticated. The server response was: 5.7.0 Authentication Required. Learn more at.

    private void SendMail(string email, string firstname)
    {
       
        MailAddress from = new MailAddress($"{email}", $"{firstname}");
       
        MailAddress to = new MailAddress($"{email}");
       
        MailMessage m = new MailMessage(from, to);
       
        m.Subject = "TEST";
       
        m.Body = "<h2>TEST</h2>";
       
        m.IsBodyHtml = true;
       
        SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587);
       
        smtp.Credentials = new NetworkCredential("jewralyapp@mail.ru", "password");
        smtp.EnableSsl = true;
        smtp.Send(m);
    }

I want to send a letter to the mail, but the error that I indicated above comes out, here is the code, can you tell me what is wrong?

Did you check one of the many duplicates you find here in StackOverflow, e.g. https://stackoverflow.com/questions/18503333/the-smtp-server-requires-a-secure-connection-or-the-client-was-not-authenticated. — Klaus Gütter, Jun 06 '21 at 19:24

score 0 · Answer 1 · answered Jun 06 '21 at 19:22

I see that your email is @mail.ru and the server is gmail, is that correct? I think you need to use your gmail account. You also need enable weaker credentials on your gmail account. Forgot what they actually call it but it's on gmail security setting.

score 0 · Answer 2 · edited Mar 04 '22 at 09:46

0

I had also faced the same problem.

Your SmtpClient is gmail, but you are using "jewralyapp@mail.ru"!!!
Make sure to set "Less secure app access" to ON in your Gmail security setting.

In my case, the problem was solved.

edited Mar 04 '22 at 09:46

ouflak

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answered Feb 27 '22 at 07:38

Saeed.Sabzi

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C#. SMTP The server response was: 5.7.0 Authentication Required

2 Answers2