无法通过 ASP.NET 应用程序发送电子邮件

Question

我有一个在专用服务器“Windows Server 2012 R2”上运行的 ASP.NET 应用程序。该网站自始至终使用 SSL 加密，证书已正确安装在服务器上，并在通过不同浏览器访问时显示为有效。

我现在想通过我的应用程序发送电子邮件，为此我按照本文中的说明设置了一个 SMTP 服务器。 http://www.vsysad.com/2014/09/setup-and-configure-smtp-server-on-windows-server-2012/

按照上面指定的设置 SMTP 服务器后，我可以使用 powershell 发送电子邮件，并且发送没有问题。但是，当我通过我的应用程序执行相同操作时，我收到以下错误

Exception Type: System.Security.Authentication.AuthenticationException
Exception: The remote certificate is invalid according to the validation procedure.
Stack Trace: 
   at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, Exception exception)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
   at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.Mail.SmtpConnection.Flush()
   at System.Net.Mail.EHelloCommand.Send(SmtpConnection conn, String domain)
   at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at EmailSender.SendMailSingleRecipient(String recipient, String subject, String message)

从我的应用程序发送电子邮件的代码非常简单，如下所示。

MailMessage mailMessage = new MailMessage();
mailMessage.From = new MailAddress("no-reply@mysite.com");
mailMessage.To.Add("myemail@email.com");
mailMessage.Subject = "subject"
mailMessage.Body = "message"

SmtpClient smtpClient = new SmtpClient("localhost", 25);
smtpClient.Send(mailMessage);

我已经多次看到相同的问题被报告，但没有任何答案可以为我解决问题。有人可以解释此错误背后的原因以及可能的原因/解决方案。

Answer 1

我设法找到了原始问题的解决方案。我没有直接从我的应用程序发送，而是将我的 SMTP 服务器设置为使用拾取目录。

现在应用代码很简单，指定送货方式和取货目录也可以移到配置文件中。

SmtpClient client = new SmtpClient("localhost", 25);
client.DeliveryMethod = SmtpDeliveryMethod.SpecifiedPickupDirectory;
client.PickupDirectoryLocation = @"C:\inetpub\mailroot\Pickup";
client.Send(mail);

这种方法的另一个优点是无需在开发机器上设置 SMTP 即可测试从应用程序生成的电子邮件。通过查看拾取目录，您可以确定应用程序是否正常工作。

在我的实时服务器上使用这种方法，我几乎一从我的应用程序发送电子邮件就收到了电子邮件，因此性能非常好。

Answer 2

检查此功能。

protected void SendMail()
    {
        var fromAddress = "youremail@gmail.com";// Gmail Address from where you send the mail
        var toAddress = YourEmail.Text.ToString();
        const string fromPassword = "password";//Password of your gmail address
        string email = YourEmail.Text.ToString();
        string body = "First Name: " + YourName.Text + "\n";
        body += "Last Name: " + YourlName.Text + "\n";
        body += "Email: " + YourEmail.Text + "\n";
        body += "mobile no.: " + Yourmobi.Text + "\n";
        body += "Question: \n" + Comments.Text + "\n";
        var smtp = new System.Net.Mail.SmtpClient();
        {
            smtp.Host = "smtp.gmail.com";
            smtp.Port = 587;
            smtp.EnableSsl = true;
            smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
            smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
            smtp.Timeout = 20000;
        }
        smtp.Send(toAddress, fromAddress, email, body);
        try
        {
            lblMsgSend.Text = "Your Comments after sending the mail";
            lblMsgSend.Visible = true;
            Yourmobi.Text = "";
            YourEmail.Text = "";
            YourName.Text = "";
            YourlName.Text = "";
            Comments.Text = "";
        }
        catch (Exception) { }
    }

Answer 3

这可能是服务器上的 SMTP 服务没有使用与 https 相同的证书。

diagnostic steps I had read here

Answer 4

问题是，你需要设置Credentials。您的 powershell 脚本似乎在您的 asp.net 主机之外的另一个用户上下文中运行，因此它可以工作，但您的 asp.net 应用程序不能。

随便看看：How to set username and password for SmtpClient object in .NET?