DeliveryNotificationOptions.Never is not working?

Question

We have been using Mail.dll for a long time now. We have noticed that a lot of our email are undelivered. The point is we are getting to many emails back like "Undeliverable: Your email was not Delivered".

These email just fill our inbox but we do not care about it and we do not want such bounce responses.

I tried the following to try to stop such emails by following this link.
https://www.limilabs.com/blog/requesting-delivery-status-notifications-dsn

using (Smtp smtp = new Smtp())
{
    smtp.Connect("smtp.example.com");
    smtp.UseBestLogin("user", "password");
    smtp.Configuration.DeliveryNotification 
        = DeliveryNotificationOptions.Never;

    IMail email = Fluent.Mail.Text("Some text")
        .Subject("Some subject")
        .From(new MailBox("from@example.com"))
        .To(new MailBox("to@example.com"))
        .Create();

    smtp.SendMessage(email);

    smtp.Close();
}

But I am still getting such bounce email back. Please help. Thanks

Answer 1

Mail.dll sends this configuration parameter to your SMTP server. E.g.:

S: RCPT TO:<test@example.com> NOTIFY=NEVER

This options is available and used only if SmtpExtension.DSN is reported by Smtp.SupportedExtensions().

You server might be not supporting this extension.

Also if your server simply ignores it there's nothing you or Mail.dll can do about it. You can only turn on logging and make sure that NOTIFY parameter is included.