在 c# windows 应用程序中从雅虎发送邮件时出现身份验证错误

Question

i am trying to send email from my software using the smtp of yahoo but it shows the following error "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Authentication required".

I know about the less secure apps setting in google but i don't know about the settings in yahoo. the same code runs fine with the gmail account credentials. here is the code for reference.

string EmailFrom = "test@yahoo.com";
        string EmailTo = "test@gmail.com";
        string PassWord = "test123";
        string EmailHost = "smtp.mail.yahoo.com";
        string status = "";
        string Body = "";

        MailMessage message = new MailMessage();
        SmtpClient smtp = new SmtpClient();

        message.From = new MailAddress(EmailFrom);
        message.To.Add(new MailAddress(EmailTo));
        message.Subject = "Auto Backup at test" ;
        message.Body = "Backup has been taken at test on" + DateTime.Now;
        Body = "Backup has been taken at test on" + DateTime.Now;
        smtp.Port = 587;
        smtp.Host = EmailHost;
        smtp.EnableSsl = true;
        smtp.UseDefaultCredentials = false;
        smtp.Credentials = new NetworkCredential(EmailFrom, PassWord);
        smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
        //ServiceLogLibrary.WriteErrorlog("Step:5");
        //Library.WriteErrorlog("Before sending mail");
        smtp.Send(message);

Answer 1

Just providing some more information here as things have changed a little since the accepted answer was posted.

1. Go to the account security settings ( https://login.yahoo.com/account/security )
2. Scroll to the bottom and search for the "Manage app passwords" heading as shown below and click it to add a new app.

3. Select an app type and generate the password. For API apps, use "Other App".

4. Use this password instead of your standard mailbox password when sending emails via your SmtpClient.

Answer 2

You need to go to

1. Go to your "Account security" settings.
2. Select Allow apps that use less secure sign in.
3. To deny or turn off app access, deselect the undesired app.

Source: Temporarily allow or deny access to apps using older security sign in