c# gmail connection failed because connected host has failed to respond

Question

I'm trying to send a mail with my gmailaccount from a server with the following code.

            var fromAddress = new MailAddress("xxxxx@gmail.com", "xxxxxx");
        var toAddress = new MailAddress(toMailAddress);
        const string fromPassword = "xxxxx";

        var smtp = new SmtpClient
        {
            Host = "smtp.gmail.com",
            Port = 587,
            EnableSsl = true,
            DeliveryMethod = SmtpDeliveryMethod.Network,
            UseDefaultCredentials = false,
            Credentials = new NetworkCredential(fromAddress.Address, fromPassword)
        };
        using (var message = new MailMessage(fromAddress, toAddress)
        {
            IsBodyHtml = true,
            Subject = mailSubject,
            Body = htmlBody
        })
        {
            smtp.Send(message);
        }

This gives the next result when I deploy it on my windows server although I have an Inobound Rule for port 587 on the firewall. It works perfect when I test it local

connectionFailed

take a look at this question also learn to use the debugger to step through your code - [Sending Mail to Gmail Account using C#](https://stackoverflow.com/questions/29251189/sending-mail-using-gmail-smtp-from-csharp-net) — MethodMan, Jul 17 '17 at 19:13
Possible duplicate of [Sending email through Gmail SMTP server with C#](https://stackoverflow.com/questions/704636/sending-email-through-gmail-smtp-server-with-c-sharp) — S.Dav, Jul 17 '17 at 20:21
Per OPs own comment on the strangely accepted answer below, I'm voting to close this as too localised, because it was solved by the OPs hosting company opening a port in the firewall. — J. Steen, Jul 21 '17 at 08:29

score -1 · Accepted Answer · answered Jul 17 '17 at 20:02

-1

I too have faced this problem. Actually Gmail does not allow to access gmail for sending mails for less secure apps. Perform the following steps: if you are getting exception like

"An unhandled exception of type 'System.Net.Mail.SmtpException' occurred in System.dll

Additional information: 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"

Go to your google account "My Account".
under "Sign-in & security" go to the bottom, you will find "Allow less secure apps: OFF", you need to turn it on by clicking the button next to it.
Now your gmail account will be accessible from your code.

answered Jul 17 '17 at 20:02

Pranav Mishra

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Sadly this isn't the solution. "Allow less secure apps" is already turned on. I don't think I works local if it's turned off. – Lieven Jul 18 '17 at 06:44
Please share complete exception u are getting – Pranav Mishra Jul 18 '17 at 06:46
You'll find the exception here: https://i.stack.imgur.com/bBqff.png – Lieven Jul 18 '17 at 06:55
are you also using some socket in your code? if yes see whether it is accessible or not. Try pinging the address you are trying to connect using socket from the environment you are using it. – Pranav Mishra Jul 18 '17 at 07:01
Not using any socket in code. Just the code above. Pinging to 108.177.119.109 works fine from the server. – Lieven Jul 18 '17 at 07:06
did you try changing port? – Pranav Mishra Jul 18 '17 at 07:25
It seems that my hosting company was blocking port 587. Problem is solved now – Lieven Jul 18 '17 at 12:08
Nice how did it solve? – Pranav Mishra Jul 18 '17 at 12:10
The company where the server is hosted, told me that they standard block this port. On my request they opened it for this specific server. Thanks for all investigation. – Lieven Jul 18 '17 at 12:20

c# gmail connection failed because connected host has failed to respond

1 Answers1