如何使用TLS和System.Net.Mail.SMTPCLient连接到googlemail.com？

Question

I'm testing a normally working emailing module (.Net 4.5.2, C#) based on the System.Net.Mail.SmtpClient class, to which I have added support for TLS. To do this I'm trying to connect to my personal googlemail.com account using the same smtp settings that I use in my browser. I've set up the SmtpClient object as

SmtpClient mailer = new SmtpClient(); 
mailer.Host = "tls://smtp.gmail.com"; 
mailer.Credentials = new System.Net.NetworkCredential("me@googlemail.com","myGooglemailPassword"); mailer.EnableSsl = true;
mailer.UseDefaultCredentials = true; // although msdn states that this is necessary for TLS, it doesn't actually seeme to make any difference 
mailer.Port = 587; 
var message = new MailMessage();
message.Subject="dontcare"; 
message.Body = "dontcare"
message.To.Add("me@googlemail.com"); 
message.From = new MailAddress("myBusinessEmailaddress@somewhere"); 
mailer.Send(message);

The problem is that this is rejected by gmail with the error

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

Given that my gmail account works normally for me otherwise, what am I missing in the .Net implementation?

Answer 1

The problem was that by default Googlemail/Gmail blocks email sources that it deems to be 'less secure' (Outlook is an example). You have to turn this off in the Gmail account settings, and then the problem disappears.