使用带有Mandrill SMTP的SmtpClient进行.NET发送失败

Question

当以下代码中的mailFromName包含“æ”，“ø”或“å”时，我们正面临通过Mandrill SMTP发送邮件时出现问题的无效问题。当我们使用另一个SMTP时，邮件发送得非常好。

Mail.ReplyToList.Add(New MailAddress(mailFromAddress, mailFromName, System.Text.Encoding.UTF8))

我们使用.NET smtpClient类。

Dim SmtpClient As New System.Net.Mail.SmtpClient
SmtpClient.Send(Mail)
SmtpClient.Dispose()

更新

正如评论中所建议的那样，我同意这看起来像编码问题，但无法看到我能为自己做些什么。

它似乎只连接到包含æ，ø和å而不是Mail.To的RepleyToList，我以类似的方式定义它：

Dim mTo As New MailAddress(mailToAddress, mailToName, System.Text.Encoding.UTF8)
Mail.To.Add(mTo)

mailToName可以包含æ，ø和å，并且发送完全没问题。

很难证明某些事情没有发生，但我确信邮件不会发送，我确信它已连接到replyToList中的sendername。

我怎么知道？

我在发送之前记录邮件。包含相关字符的邮件会被记录，但在https://mandrillapp.com/activity中永远不会显示，并且永远不会到达收件人。我删除了æ，ø或å - 所有这些都在Mandrill概述中可见，一切正常。

想看看我的完整代码吗？

请注意，发送失败的邮件不会产生异常。

  Public Sub sendMail(ByVal mailFromAddress As String, ByVal mailFromName As String, _
                      ByVal mailToAddress As String, ByVal mailToName As String, ByVal mailCcAddress As String, ByVal mailBCcAddress As String, _
                      ByVal mailPriority As Net.Mail.MailPriority, ByVal IsBodyHtml As Boolean, ByVal mailSubject As String, _
                      ByVal bodyPlain As String, ByVal bodyHTML As String)
    Const maxtry As Integer = 3
    Dim tries As Integer = 0
    Dim failed As Boolean = False

    ' mailFromName = mailFromName.Replace("æ", "ae")

    Do
      tries += 1

      Try

        failed = False
        Dim Mail As New MailMessage


        If mailFromAddress <> String.Empty Then
          'Mail.ReplyTo = New MailAddress(mailFromAddress, mailFromName, System.Text.Encoding.UTF8)
          Mail.ReplyToList.Add(New MailAddress(mailFromAddress, mailFromName, System.Text.Encoding.UTF8))
        Else
          'Mail.ReplyTo = New MailAddress(Me.MailAddressFrom, Me.MailAddressDisplayName, System.Text.Encoding.UTF8)
          Mail.ReplyToList.Add(New MailAddress(Me.MailAddressFrom, Me.MailAddressDisplayName, System.Text.Encoding.UTF8))
        End If
        Mail.From = New MailAddress(Me.MailAddressFrom, Me.MailAddressDisplayName, System.Text.Encoding.UTF8)
        Mail.Sender = New MailAddress(Me.MailAddressFrom, Me.MailAddressDisplayName, System.Text.Encoding.UTF8)

        If mailToAddress <> String.Empty Then
          Dim mTo As New MailAddress(mailToAddress, mailToName, System.Text.Encoding.UTF8) 'UTF8
          Mail.To.Add(mTo)
        End If
        If mailCcAddress <> String.Empty Then
          Dim mCc As New MailAddress(mailCcAddress)
          Mail.CC.Add(mCc)
        End If
        If mailBCcAddress <> String.Empty Then
          Dim mBCc As New MailAddress(mailBCcAddress)
          Mail.Bcc.Add(mBCc)
        End If

        Mail.Priority = mailPriority

        Mail.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure

        Mail.IsBodyHtml = IsBodyHtml 
        Mail.HeadersEncoding = Encoding.GetEncoding("utf-8")

        Mail.Subject = mailSubject
        Mail.SubjectEncoding = Encoding.GetEncoding("utf-8") ' = System.Text.Encoding.Default 'UTF8 'Default ' Test on all possible encodings

        If IsBodyHtml Then
          Mail.AlternateViews.Add(AlternateView.CreateAlternateViewFromString(bodyHTML, System.Text.Encoding.Default, "text/html"))
        End If
        Mail.BodyEncoding = Encoding.GetEncoding("utf-8")
        Mail.Body = bodyPlain

        ' Add to log
        addToMailLog(mailToAddress, mailCcAddress, mailSubject, bodyPlain)

        ' Send
        Dim SmtpClient As New System.Net.Mail.SmtpClient
        'SmtpClient.ServicePoint.MaxIdleTime = 1
        SmtpClient.Send(Mail)
        Me._status = EMailStatus.EOkay
        SmtpClient.Dispose()

      Catch ex As Exception
        Dim debugInfo As New CDebug("sendMail", "Try: " & tries.ToString & ", UserId: " & Me.UserId, ex.ToString, Me.UserId, String.Empty)
        Me._status = EMailStatus.EMailSendError
        failed = True
      End Try

    Loop Until (failed = False Or tries >= maxtry)

  End Sub

更新II

我现在使用WireShark跟踪SMTP通信。请参阅屏幕截图，其中显示了未交付但未显示在Mandrill活动列表中的邮件的通信 - 即使我们获得SMTP响应正常并排队ID。

我有三个例子：

送达：

mailFromName = "xxx xxxxxxxxx xxxx - xxxxxxxxxx xxxxxxx xxxxxxxxx"

未交付：

mailFromName = "xxx xxxxxxxxx xxxx - xxxxxxxxxx xxxxxxx xxxxxxæxx"

送达：

mailFromName = "æxx xxxxxxxxx xxxx - xxxxxxxxxx xxxxxxx xxxxxxxxx"

Answer 1

我相信我已经找到了解释。似乎smtpclient在约72个字符的主题和回复显示名称后添加一个新行。问题是这似乎是在字符串编码后发生的。因此，在某些情况下，在编码字符的中间添加一个新行字符，其中afaik是非法的。

我不确定为什么Mandrill SMTP服务器在没有返回错误的情况下失败，而其他SMTP服务器处理这种情况就好了。

既然我明白了发生了什么，我必须想办法解决它 - 最好的建议得到赏金。