C # SmtpClient class not able to send email using gmail

Question

I'm having trouble sending emails using my gmail account. I pull my hair out.

The same settings work fine in Thunderbird.

Here is the code. I also tried port 465 with no luck.

SmtpClient ss = new SmtpClient("smtp.gmail.com", 587); ss.Credentials = new NetworkCredential("username", "pass"); ss.EnableSsl = true; ss.Timeout = 10000; ss.DeliveryMethod = SmtpDeliveryMethod.Network; ss.UseDefaultCredentials = false; MailMessage mm = new MailMessage("[e-mail]", "[e-mail]", "subject here", "my body"); mm.BodyEncoding = UTF8Encoding.UTF8; mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure; ss.Send(mm); 

Gets an error

"A secure connection is required for the SMTP server or the client failed authentication. Server response: 5.5.1 Authentication is required. Read more in the section

Gets a stack trace

  at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net.Mail.MailCommand.Send(SmtpConnection conn, Byte[] command, String from) at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at email_example.Program.Main(String[] args) in C:\Users\Vince\Documents\Visual Studio 2008\Projects\email example\email example\Program.cs:line 23 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() 

Answer 1

You will not believe that fixed my problem.

Credentials Property

 ss.Credentials = new NetworkCredential("username", "pass"); 

to be announced after

 ss.UseDefaultCredentials = false; 

Thus, the final list of work codes

 SmtpClient ss = new SmtpClient("smtp.gmail.com", 587); ss.EnableSsl = true; ss.Timeout = 10000; ss.DeliveryMethod = SmtpDeliveryMethod.Network; ss.UseDefaultCredentials = false; ss.Credentials = new NetworkCredential("username", "pass"); MailMessage mm = new MailMessage("[e-mail]", "[e-mail]", "subject here", "my body"); mm.BodyEncoding = UTF8Encoding.UTF8; mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure; ss.Send(mm); 

This is mistake?

Answer 2

stack overflow

In your case, this means that you must send it with the email address with which you are logged in to Google.

stack overflow

So there may be a firewall that interferes with the connection. I am facing this problem right now while checking your code. Try the suggested TELNET test.

Answer 3

Work with me only with port 25.

Answer 4

It works, but it is not very convenient. Check out the .SendAsync client: http://msdn.microsoft.com/en-us/library/x5x13z6h.aspx

Usage example:

  var message = new MailMessage("from", "to", "subject", "body"); var client = new SmtpClient("smtp.gmail.com", 587) { Credentials = new NetworkCredential("login", "password"), EnableSsl = true }; client.SendCompleted += (s, e) => { client.Dispose(); message.Dispose(); }; client.SendAsync(message, null); 

Answer 5

This work is excellent. Create a letter template in a separate MailTemplate.html file.

Add genuine NetworkCredentials - username and password

 private void SendMail() { string filename = Server.MapPath("~/MailTemplate.html"); string username = UserName.Text.ToString(); string mailbody = System.IO.File.ReadAllText(filename); mailbody = mailbody.Replace("##NAME##", username); string to = Email.Text; string from = "[e-mail]"; MailMessage message = new MailMessage(from, to); message.Subject = "Auto Response Email"; message.Body = mailbody; message.BodyEncoding = Encoding.UTF8; message.IsBodyHtml = true; SmtpClient client = new SmtpClient("smtp.gmail.com", 587); System.Net.NetworkCredential basicCredential = new System.Net.NetworkCredential("[e-mail]", "test123#"); client.EnableSsl = true; client.UseDefaultCredentials = true; client.Credentials = basicCredential; try { client.Send(message); SuccessMessage.Text = "Email Sending successfully"; } catch (Exception ex) { ErrorMessage.Text = ex.Message.ToString(); } } 

MailTemplate.html

 <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>Title</title> </head> <body> <div style="border: thin solid #0066FF; width: 550px; margin: 25px auto; padding: 15px; font-family: 'Microsoft Himalaya'; font-size: x-large; font-style: normal; color: #0066FF; background-color: #EfEFF2;"> <br /> <p style="vertical-align: middle">Dear ##NAME##,</p> </div> </body> </html> 

Answer 6

I can verify that setting UseDefaultCredentials to false MUST be done before NetworkCredentials are created. I had the same problem.

Answer 7

It works fine in my case:

 private void btnTestConnection_Click(object sender, EventArgs e) { btnTestConnection.Enabled = false; SmtpClient ss = new SmtpClient(txtSmtpHostName.Text.Trim(), Convert.ToInt32(numSmtpHostPort.Value)); ss.EnableSsl = chkSmtpSecureType.Checked; ss.Timeout = 10000; ss.DeliveryMethod = SmtpDeliveryMethod.Network; ss.UseDefaultCredentials = false; ss.Credentials = new NetworkCredential(txtSmtpAccount.Text.Trim(), txtSmtpPassword.Text); MailMessage mm = new MailMessage(txtSmtpFromEmail.Text.Trim(), "[e-mail]", "subject", "my body"); mm.BodyEncoding = UTF8Encoding.UTF8; mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure; ss.SendCompleted += (s, b) => { ss.Dispose(); mm.Dispose(); }; try { ss.Send(mm); ss.Dispose(); mm.Dispose(); MessageBox.Show("Connection successfully"); } catch (Exception ep) { MessageBox.Show("Connection error: " + ep.Message, "Smtp Connection Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } btnTestConnection.Enabled = true; }