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vb.net - 在内部交换 smtp 服务器上使用 system.net.mail 的大量消息超时

转载 作者:行者123 更新时间:2023-12-04 05:02:10 24 4
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我正在制定一个计划,每周向我们公司的每位销售员工发送提醒/更新。每周大约 120 个,自动化,在短时间内。这是一个内部程序,仅供内部收件人使用,我不担心垃圾邮件或不需要的邮件,也不能取消订阅。每条消息都是根据每个销售人员的客户列表为他们个性化的,并包含每周“要做”的项目,供他们调用客户。

我在内部运行 Exhange 2007,并为我的开发环境和运行这些自动化项目的服务器提供一个开放的内部 SMTP 连接器。该程序对一两个商店运行良好,但是当我为每个商店运行它时,我在发送了 110 条消息后在某处超时。

当我遍历销售人员列表并进行各自的查找和消息构建时,我并没有尝试将邮件排队或将它们保存在块中,我尝试使用以下子发送消息。

Sub doMail(ByRef MessageBody As String, ByVal nameString As String, ByVal sendTo As ArrayList, Optional ByVal markurgent As Boolean = False, _
Optional ByVal sendCC As ArrayList = Nothing, Optional ByVal sendBcc As ArrayList = Nothing)
Try
' Setup Mail Message
Dim oClient As SmtpClient = New SmtpClient(ConfigurationManager.AppSettings("mail_server").ToString())
oClient.Timeout = 20000
'oClient.Port = 50747
Dim objMessage As New MailMessage()
objMessage.From = New System.Net.Mail.MailAddress(ConfigurationManager.AppSettings("mail_from_address").ToString, ConfigurationManager.AppSettings("mail_from_name").ToString)
objMessage.Subject = String.Format("Weekly Hitlist Report ~ {0}", nameString)

If (ConfigurationManager.AppSettings("debugMode").ToString() = 1) Then
Dim debugSB As StringBuilder = New StringBuilder

For Each s As String In sendTo
debugSB.AppendLine(String.Format("To: {0}<br>", s))
Next
For Each s As String In sendCC
debugSB.AppendLine(String.Format("cc: {0}<br>", s))
Next
For Each s As String In sendBcc
debugSB.AppendLine(String.Format("bcc: {0}<br>", s))
Next
MessageBody = String.Format("Debug Mode is Active. <br> {0} <br><hr noshade>{1}", debugSB.ToString, MessageBody)
objMessage.To.Add(ConfigurationManager.AppSettings("mail_to_address").ToString)
Else
For Each receiver As String In sendTo
Try
objMessage.To.Add(receiver.Trim())
Catch ex As Exception
' do nothing
End Try
Next
For Each receiver As String In sendCC.ToArray
Try
objMessage.CC.Add(receiver.Trim())
Catch ex As Exception
' do nothing
End Try
Next
For Each receiver As String In sendBcc
Try
objMessage.Bcc.Add(receiver.Trim())
Catch ex As Exception
' do nothing
End Try
Next
End If



objMessage.Body = MessageBody
objMessage.Priority = IIf(markurgent, MailPriority.High, MailPriority.Normal)
objMessage.IsBodyHtml = True
oClient.Send(objMessage)
oClient = Nothing
Console.WriteLine(String.Format("{1} - message sent - {0} ", nameString, Now()))
Catch ex As Exception
Console.WriteLine(ex.Message)
Console.WriteLine("****************")
Console.WriteLine(ex.StackTrace)
End Try
End Sub

我试图将客户端超时增加到 20 秒,并且我试图通过将其设置为空来明确地尝试在每条消息之后关闭与邮件服务器的客户端连接。

一切看起来都很顺利,直到最后,我已经从下面的输出片段中删除了我们的销售人员姓名。现在一切都来找我,因为我在 Debug模式下运行它,我们还没有尝试对整个公司进行实时运行,所以我不知道是否是因为一切都将发送给一个收件人。

在我收到错误(连接超时)并且系统恢复后,我会收到在异常之后并且仅在程序终止之后发送的任何消息。在 .NET 的早期版本中,我知道在发送消息之前程序必须退出或线程必须结束,但我正在使用的其他程序我通常不再在 .NET 4 中使用它。

输出包括错误;第一部分已被剪掉
 ...
4/15/2013 9:46:36 AM - message sent -
4/15/2013 9:46:41 AM - message sent -
4/15/2013 9:46:46 AM - message sent -
4/15/2013 9:46:51 AM - message sent - Store 14 Unassigned
4/15/2013 9:46:56 AM - message sent -
4/15/2013 9:47:01 AM - message sent -
4/15/2013 9:47:06 AM - message sent -
4/15/2013 9:47:11 AM - message sent -
4/15/2013 9:47:16 AM - message sent -
4/15/2013 9:47:21 AM - message sent -
4/15/2013 9:47:26 AM - message sent -
4/15/2013 9:47:31 AM - message sent -
4/15/2013 9:47:36 AM - message sent -
4/15/2013 9:47:41 AM - message sent -
Service not available, closing transmission channel. The server response was: 4.4.1 Connection timed out
****************
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 HitListRunner_Main.Module1.doMail(String& MessageBody, String nameString, ArrayList sendTo, Boolean markurgent, ArrayList sendCC, ArrayList sendBcc) in C:\Users\markl\Documents\Visual Studio 2010\Projects\HitListRunner\HitListRunner-Main\Module1.vb:line 391
4/15/2013 9:47:46 AM - message sent - Store 20 Unassigned
4/15/2013 9:47:51 AM - message sent - Store 98 Unassigned
4/15/2013 9:47:58 AM - message sent - !! - UNDETERMINED LIST - !!
ending - enter to exit

我还尝试为每个单独的商店和较小的子集发送。当我一次为整个公司竞选时,我只会收到此错误。

我在 Exchange 中没有看到任何禁止这样做的内容,也没有看到等待的高消息队列。关于发送消息的不同方法或其他尝试的任何建议? (我不想使用第 3 方 dll 或外部组件)。

最佳答案

我经历过这个问题的痛苦。经过 2 年的研究,我无法确定我的 .net 应用程序出现问题的确切原因。有许多问题和实现选项将有助于最大限度地减少此异常(exception)的影响。我们现在处于这个问题不会以明显的方式影响最终用户的程度。

  • 您需要确保在 *.config 中设置了一些 SMTP 配置变量,以帮助将应用程序调整到您的环境。 SMTP 客户端超时、重试尝试、重试之间的时间等。我们发现尝试之间大约有 20 秒,在完全停止工作之前大约有 5 次尝试。
  • 您将需要实现日志记录机制来记录它们发生的时间和频率,以便您可以设置上面的变量。我正在寻找来自机器和服务器事件日志的电子邮件量、时间、服务包安装、病毒检查程序或防火墙干扰,以尝试找出原因。
  • 实现非 Blockingcollection管理所有电子邮件的发送,因为如果您通过代码发送大量邮件,您将遇到 SMTP 4.4.1 超时错误。这是一个 producer consumer模式,我发现这是一个相对容易实现的实现,并且非常成功地解决了这个问题。队列允许您确保最终发送电子邮件。如果你想要一个完整的故障安全,你也可以将该队列持久化到磁盘。我们永远不需要回到那段代码上。
  • 如果没有第三方工具,伪造或模拟 .net SMTP 实现以针对此问题对您的代码进行单元测试并不容易。我没有走这条路,因为在一天结束时,有太多我无法控制的部分。基本上我只是假设它总是会失败,并且我放置了很多后备选项来等待问题自行解决。

  • 我们尝试过的事情似乎对 4.4.1 超时异常的频率没有影响。
  • 限制电子邮件发送到交换的速率。
  • 更改发送时间(也就是非工作时间)
  • 将电子邮件分成小块,然后通过垃圾收集从内存中清除所有 .net 组件。

  • 希望有帮助。

    代码片段
    ''' <summary>
    ''' Provide a mechanism to throttle the subsequent attempts to send emails.
    ''' </summary>
    ''' <param name="emailAddress"></param>
    ''' <param name="attemptNumber"></param>
    ''' <remarks>Need to implement a more dynamic function as attempts persist, pause for longer for a number of attempt, then add the email to a failed queue.</remarks>
    Private Shared Sub RestBeforeSendingAgain(ByVal emailAddress As String, ByVal attemptNumber As Integer)

    If attemptNumber > 1 Then

    ' Wait 30 seconds in between every attempt, or the value configured in the config file.
    Dim retryIntervalInSeconds As Integer = 30
    If Not String.IsNullOrEmpty(System.Configuration.ConfigurationManager.AppSettings.Item("SMTPFailureReTryIntervalInSeconds")) Then
    Integer.TryParse(System.Configuration.ConfigurationManager.AppSettings.Item("SMTPFailureReTryIntervalInSeconds"), retryIntervalInSeconds)
    End If
    logger.Warn("Problem emailing {0}. Waiting {1} seconds to help clear technical issues.", emailAddress, retryIntervalInSeconds.ToString)
    System.Threading.Thread.Sleep(System.TimeSpan.FromSeconds(retryIntervalInSeconds))

    End If
    End Sub

    ''' <summary>
    ''' Attempt to send an email message and record any issues with that mailmessage to the application log.
    ''' Allows the process to know the success or failure of that approach.
    ''' </summary>
    ''' <param name="mailClient"></param>
    ''' <param name="mailMessage"></param>
    ''' <param name="attemptNumber"></param>
    ''' <returns>The success or failure of the SMTP server to send the message without causing an error.</returns>
    ''' <remarks></remarks>
    Private Shared Function AttemptToSendEmail(ByRef mailClient As System.Net.Mail.SmtpClient, ByRef mailMessage As MailMessage, ByVal attemptNumber As Integer) As Boolean
    Dim result As Boolean = False
    Try
    logger.Trace("Started: AttemptToSendEmail", attemptNumber)

    RestBeforeSendingAgain(mailMessage.To.ToString, attemptNumber)
    mailClient.Send(mailMessage)
    result = True

    Catch smtpEx As SmtpException
    result = False
    logger.ErrorException(String.Format("{3}{1}{0}{1}{2}", ExceptionFormater.FormatException(smtpEx), Environment.NewLine, ExceptionFormater.FormatStack(smtpEx), "AttemptToSendEmail failed with Smtp exception."), smtpEx)

    Catch ex As Exception
    result = False
    logger.ErrorException(String.Format("{3}{1}{0}{1}{2}", ExceptionFormater.FormatException(ex), Environment.NewLine, ExceptionFormater.FormatStack(ex), "AttemptToSendEmail failed with generic exception."), ex)

    Finally

    If result Then
    logger.Trace("Succeeded: To email {0} on attempt {1}.", mailMessage.To.ToString, attemptNumber)
    Else
    logger.Warn("Failed: To email {0} on attempt {1}.", mailMessage.To.ToString, attemptNumber)
    End If

    End Try

    Return result

    End Function

    ' Configure the timeout in milliseconds from the App.Config file.
    ' 200 seconds = 200,000 miliseconds
    MySmtpClient.Timeout = CInt(TimeSpan.FromSeconds(SmtpClientTimeoutSeconds).TotalMilliseconds)

    关于vb.net - 在内部交换 smtp 服务器上使用 system.net.mail 的大量消息超时,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16019264/

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