Can't auth to Gmail smtp via MailMessage & smtpClient

Question

I cannot figure out for the life of my why this isn't working

SmtpClient smtp = new SmtpClient
{
    Host = "smtp.gmail.com",
    Port = 587,
    UseDefaultCredentials = false,
    DeliveryMethod = SmtpDeliveryMethod.Network,
    Credentials = new NetworkCredential("[email protected]", "myGmailPasswordHere"),
    EnableSsl = true,
    Timeout = 10000
};


smtp.Send(mail);

I get:

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

I just specified EnableSsl to true so that shouldn't be the issue in terms of secure connection.

I'm running this from localhost. And yes, my username and password I'm entering to auth (my gmail account credentials) is 100% right.

Answer 1

If login info is 100% right, you need to set UseDefaultCredentials = false first and then set the credentials you want to use Credentials = new NetworkCredential("[email protected]", "myGmailPasswordHere").

If you set the credentials first, when you set UseDefaultCredentials = false this will make the Credentials property to null.

This is wired, but it happened to me.

Debug your code and check if the Credentials property is null before you call smtp.Send(message);. If so, then try inverting the order. It seems you have it in the right order, but if it's null, don't use the inline initialization.

Hope it helps.

EDIT: If you are using two-step verification, be sure you are using an App Specific password

Answer 2

I know this is an old topic, BUT... Google has changed something on their security settings.

Was struggling with all the answers until I checked my email with a mail from Google stating that "we've recently blocked a sign-in attempt on your Google account".

That led me to this page: Google Account Security

Under the "Access for less secure apps" section, you can enable access to your account from other devices/applications... like your C# application.

Note, there is no longer an "application specific" section.

Hope this helps someone... I just lost 30 minutes of my life...

Answer 3

It looks like Gmail requires Application-specific password(not your main password).

Please, look into this: http://support.google.com/mail/bin/answer.py?hl=en&answer=1173270

I had the same problem recently.

Answer 4

This worked just fine for me

SmtpClient smtp = new SmtpClient
    {
        Host = "smtp.gmail.com",
        Port = 587,
        UseDefaultCredentials = false,
        DeliveryMethod = SmtpDeliveryMethod.Network,
        Credentials = new NetworkCredential("[email protected]", "mypassword"),
        EnableSsl = true,
        Timeout = 10000
    };

    MailMessage message = new MailMessage();
    message.Body = "hello there";
    message.Subject = "hi!!";
    message.To.Add("[email protected]");
    message.From = new MailAddress("[email protected]");
    smtp.Send(message);