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I have never implemented Google Captcha before, so I am unaware of what the problem is. When I submit the form, sometimes it works and sometimes it doesn't. If I submit the form without checking the captcha box and then click the captcha box when it sends me back to the page, it does not send the email. Any idea on how I can fix this issue?

What I have tried:

My code behind:

protected static string ReCaptcha_Key = "<key>";
protected static string ReCaptcha_Secret = "<key>";

public bool IsReCaptchValid()
    var result = false;
    var captchaResponse = Request.Form["g-recaptcha-response"];
    var secretKey = ReCaptcha_Secret;
    var apiUrl = "{0}&response={1}";
    var requestUri = string.Format(apiUrl, secretKey, captchaResponse);
    var request = (HttpWebRequest)WebRequest.Create(requestUri);

    using (WebResponse response = request.GetResponse())
        using (StreamReader stream = new StreamReader(response.GetResponseStream()))
            JObject jResponse = JObject.Parse(stream.ReadToEnd());
            var isSuccess = jResponse.Value<bool>("success");
            result = (isSuccess) ? true : false;
    return result;

protected void btnSend_Click(object sender, EventArgs e)
    string Name = txtName.Text;
    string EmailAddress = txtEmail.Text;
    string phone = "Number not supplied";
    if(txtPhone.Text != "")
        phone = txtPhone.Text;
    string SendAddress = @"<email address>";
    string Subject = "Message from " + Name + " Top Tree Fellas Website";
    string Message = Regex.Replace(txtMsg.Text, @"\r\n?|\n", "<br />");
    if (String.IsNullOrEmpty(Name) || String.IsNullOrEmpty(EmailAddress) || String.IsNullOrEmpty(Message) || !(IsReCaptchValid()))
        lblError.Text = "Please ensure all required fields are filled in.";
            MailMessage msg = new MailMessage();
            msg.To.Add(new MailAddress(@"<email address>"));
            msg.Subject = Subject;
            msg.From = new MailAddress(SendAddress);
            msg.IsBodyHtml = true;
            msg.Body = "<p>Contact Name: " + Name + "<br />";
            msg.Body += "Email Address: " + EmailAddress + "<br />";
            msg.Body += "Phone: " + phone + "<br />";
            msg.Body += "Message:<br />" + Message + "</p>";

            msg.ReplyToList.Add(new MailAddress(EmailAddress));

            SmtpClient smtpClnt = new SmtpClient("");
            smtpClnt.UseDefaultCredentials = false;
            smtpClnt.Port = 587;
            smtpClnt.Credentials = new NetworkCredential(@"<email address>", "<password>");
            smtpClnt.EnableSsl = true;


            lblError.ForeColor = System.Drawing.Color.Green;
            txtName.Text = "";
            txtEmail.Text = "";
            txtMsg.Text = "";
            txtPhone.Text = "";
            Response.Write("<script>alert('Message sent');</script>");

        catch (Exception er)
            string er1 = er.Message + "<br />" + er.InnerException;
            lblError.Text = er1;
            Response.Write("<script>alert('Something went wrong. Please try again later or call us on: 0<phone number>');</script>");

My markup:

<script src=''></script>  
<div class="g-recaptcha" data-type="image" data-sitekey="6LfDHwcpAAAAAL71bUOZ4291MqxqDyTfvGbzOMcg"></div>
<asp:Button ID="btnSend" runat="server" ValidationGroup="vldContact" Text="Send your message" CssClass="btn btn-danger" OnClick="btnSend_Click" />
My webconfig:

        <proxy usesystemdefault = "false" bypassonlocal="false" proxyaddress=""/>

The exception I get:

Failure sending mail.
System.IO.IOException: Unable to read data from the transport connection: An established connection was aborted by the software in your host machine. ---> System.Net.Sockets.SocketException: An established connection was aborted by the software in your host machine at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags) at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) --- End of inner exception stack trace --- at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) at System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count) at System.Net.Security._SslStream.StartFrameHeader(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security._SslStream.StartReading(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security._SslStream.ProcessRead(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.TlsStream.Read(Byte[] buffer, Int32 offset, Int32 size) at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size) at System.Net.Mail.SmtpPooledStream.Dispose(Boolean disposing) at System.IO.Stream.Close() at System.IO.Stream.Dispose() at System.Net.ConnectionPool.Destroy(PooledStream pooledStream) at System.Net.ConnectionPool.PutConnection(PooledStream pooledStream, Object owningObject, Int32 creationTimeout, Boolean canReuse) at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint) at System.Net.Mail.SmtpTransport.GetConnection(ServicePoint servicePoint) at System.Net.Mail.SmtpClient.GetConnection() at System.Net.Mail.SmtpClient.Send(MailMessage message)

1 solution

That exception is nothing to do with reCAPTCHA; it's a network error in the communication between your web server and your SMTP server.

It's a generic error, with many possible causes - eg, running out of available sockets; software on the web server interfering with the connection; low-level network problems; etc.

One obvious problem: the SmtpClient class[^] is disposable. You should wrap it in a using block to ensure that its resources are always cleaned up. If you've already sent a few messages when you get the exception, that might be the cause - the sockets from the old instances haven't been closed, and you've run out of new ones.

If the using block doesn't fix it, then you're probably going to need to get your network admin to dig in to the logs to figure out what's causing the connection to be aborted. Nobody here can do that for you, as we don't have access to your computer or network.
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