Asp.net System.Net.Mail.MailMessage“Reply To”标头在IIS 6.0中被忽略，但在IIS 5.1中可以

我开发了一个web应用程序项目，并在WinXP机器IIS 5.1上进行了单元测试。它已发布到Win2003Server IIS 6.0。该应用程序的一个功能是发送一封电子邮件，邮件标题下面是一段回复。在IIS 5.1计算机上，回复将正确显示在标题中。从IIS 6.0 PC发送时，标头不包含回复地址，请参见下文：

    Public Shared Sub SendEmail_withReplyTo(ByVal emailfrom As String, _
                                        ByVal emailto As String, _
                                        ByVal vbody As String, _
                                        ByVal vsubject As String, _
                                        ByVal msgcc As String, _
                                        ByVal msgbcc As String, _
                                        ByVal sReplyTo As String)
    Dim MyMsg As New MailMessage
    ErrorTrap.ErrorMsg = Nothing
    With MyMsg
        .From = New MailAddress(emailfrom)
        .Headers.Add("Reply-To", sReplyTo)
        .To.Add(emailto)
        If msgcc.Length > 0 Then
            .CC.Add(msgcc)
        End If
        If msgbcc.Length > 0 Then
            .Bcc.Add(msgbcc)
        End If
        .Subject = vsubject
        .IsBodyHtml = True
        .Body = vbody
    End With
    Try
        Dim smtp As New SmtpClient
        smtp.Send(MyMsg)
    Catch ex As Exception
        ErrorTrap.ErrorMsg = Nothing
        ErrorTrap.ErrorMsg = ex.ToString
    End Try
End Sub

以下internet标题是从MS Outlook 2003-视图-选项粘贴的：

从装有IIS 5.1的开发人员PC上发送的对以下内容的有效回复：

缺少从MOJITO计算机发送的对IIS 6.0的2003服务器的答复：

我甚至在Win2003机器上设置了VStudio2008，并在上面代码中的一个断点处停止，以确保mailmessage实际上是正确构建的，并将Reply to添加到它的头中。然而，当到达Outlook时，来自MOJITO服务器的消息在标题中缺少回复

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是否有其他配置问题会阻碍实际代码的执行

以下是我为解决此问题所做的更改：

Dim MyMsg As New MailMessage
With MyMsg
        .From = New MailAddress(emailfrom)
        .ReplyTo = New MailAddress(sReplyTo)    'new code that fixed the problem
        '.Headers.Add("Reply-To", sReplyTo)     'old code that works on WinXP IIS 5.1 

我从Scott Mitchell的这篇伟大的文章中发现了这种替代编码方法：

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似乎这两种方法都应该奏效，但现在是继续前进的时候了

昨天在一个遗留代码保留的项目中遇到了这个问题。我想可能是这样。看起来最好相信这里的抽象。谢谢你的帮助！

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Dim MyMsg As New MailMessage
With MyMsg
        .From = New MailAddress(emailfrom)
        .ReplyTo = New MailAddress(sReplyTo)    'new code that fixed the problem
        '.Headers.Add("Reply-To", sReplyTo)     'old code that works on WinXP IIS 5.1