SmtpFailedRecipientsException Not working

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I need to check if mail was send to existing recipient

Here is my code

        try
        {
            var smtpServer = new SmtpClient("smtp.gmail.com", 587)
            {
               Credentials = new System.Net.NetworkCredential(MAIL_FROM, PASSWORD),
               EnableSsl = true
            };

            var mail = new MailMessage();
            mail.From = MAIL_FROM
            mail.To.Add(new MailAddress("[email protected]"));
            mail.Subject = title;
            mail.Body = content;
            smtpServer.Send(mailMessage);
        }
        catch (SmtpFailedRecipientsException ex)
        {
             //   never occures
        }

But SmtpFailedRecipientsException never occures when there is no recipient

Is there a way to configure SmtpServer to fire this exception?

2

There are 2 answers

2
Chris Haas On BEST ANSWER

The problem is that GMail doesn't say that the user is invalid during the SMTP transaction. The reason is that spammers used to perform dictionary attacks looking for "[email protected]" and "[email protected]", etc. Any address that didn't get marked as "not there" would then be a valid address. So most SMTP servers now just accept all addresses during the SMTP transaction and either just silently drop the invalid ones or send a bounce message later. In either case there's no way in code to determine this.

1
kavitha Reddy On
    in source view
    ------------------------------------------------------------------------------------------
            <html xmlns="http://www.w3.org/1999/xhtml">
            <head runat="server">
            <title>Send Mail using asp.net</title>
            </head>
            <body>
            <form id="form1" runat="server">
            <div>
            <table style=" border:1px solid" align="center">
            <tr>
            <td colspan="2" align="center">
            <b>Send Mail using asp.net</b>
            </td>
            </tr>
            <tr>
            <td>
            From:
            </td>
            <td>
            <asp:TextBox ID="txtFrom" runat="server"></asp:TextBox>
            </td>
            </tr>
            <tr>
            <td>
            Subject:
            </td>
            <td>
            <asp:TextBox ID="txtSubject" runat="server"></asp:TextBox>
            </td>
            </tr>
            <tr>
            <td>
            To:
            </td>
            <td>
            <asp:TextBox ID="txtTo" runat="server"></asp:TextBox>
            </td>
            </tr>
            <tr>
            <td valign="top">
            Body:
            </td>
            <td>
            <asp:TextBox ID="txtBody" runat="server" TextMode="MultiLine" Columns="30" Rows="10" ></asp:TextBox>
            </td>
            </tr>
            <tr>
            <td>
            </td>
            <td>
            <asp:Button ID="btnSubmit" Text="Send" runat="server" onclick="btnSubmit_Click" />
            </td>
            </tr>
            </table>
            </div>
            </form>
            </body>
            </html>
    ---------------------------------------------------------------------------------------In codeview
------------
         namespace  using system.net;
         btnSubmit_click(object sender,eventargs e)
        {
             MailMessage Msg = new MailMessage();
                // Sender e-mail address.
                Msg.From = txtFrom.Text;
                // Recipient e-mail address.
                Msg.To = txtTo.Text;
                Msg.Subject = txtSubject.Text;
                Msg.Body = txtBody.Text;
                // your remote SMTP server IP.
                SmtpMail.SmtpServer = "10.20.72.1";
                SmtpMail.Send(Msg);
                Msg = null;
                Page.RegisterStartupScript("UserMsg", "<script>alert('Mail sent thank you...');if(alert){ window.location='SendMail.aspx';}</script>");
                }
                catch (Exception ex)
                {
                Console.WriteLine("{0} Exception caught.", ex);
                }