后面的ASP.NET VB代码-错误服务器响应为：5.7.1客户端未通过身份验证

Question

我有一些需要发送电子邮件的ASP.NET代码，这是我在如何执行该操作时编写的过程，它尝试发送电子邮件，但是经过相当长的暂停后，出现了此完整的错误消息：

“ SMTP服务器需要安全连接或客户端未通过身份验证。服务器响应为：5.7.1客户端未通过身份验证。”

我在该站点上发现了许多类似的错误，并应用了一些修复程序，这些修复程序应允许我的代码发送电子邮件而无法正常工作。

我的ASP.NET代码在2012 r2服务器上运行，该服务器与运行Server 2008 r2和Exchange Server 2013的邮件服务器位于同一内部网络上。

可以通过“ remote.domainname.co.uk”访问ASP.NET服务器，通过“ mail.dommainname.co.uk”访问邮件服务器，其中域名是实际域名的占位符。 / p>

这是我正在使用的代码：

    Dim mailto As New MailAddress("toaddress@mydomain.com") 'My developer email add for testing.
    Dim mailfrom As New MailAddress("fromaddress@domainname.co.uk")
    Dim message As New MailMessage(mailfrom, mailto), Msg As String = ""
    Dim mailClient As New SmtpClient()
    Dim UserAndPass As New NetworkCredential()
    Dim Script = ""
    Dim n As Integer = 0
    Dim BodyText As String = ""

    Try

        message.Subject = "Issue relating to " & p.IssueDescription & "."

        'Create the body text:
        BodyText = "This email is to bring to your attention the following issue:" & NNL
        BodyText += "Building: " & p.Building & NL
        BodyText += "Location: " & p.Location & NL
        BodyText += "Issue:" & p.IssueDescription & NL
        BodyText += "Additional Information:" & NNL
        BodyText += p.AdditionalInfo & NNL
        BodyText += "Sent from the XYZ Logging System." & NL
        BodyText += "Date: " & Now.ToShortDateString & NL
        BodyText += "Time: " & Now.ToShortTimeString

        message.Body = BodyText

        'send the message
        mailClient = New SmtpClient("mail.domainname.co.uk", 25) 
        mailClient.EnableSsl = True
        mailClient.UseDefaultCredentials = False
        mailClient.Credentials = New Net.NetworkCredential("fromaddress@domainname.co.uk", "passwordtext")
        mailClient.Send(message)

        Script = "alert('"
        Script += "The Patrols Issue Email has been successfully sent!"
        Script += "')};"
        ClientScript.RegisterStartupScript(Me.[GetType](), "alert", Script, True)

    Catch ex As Exception
        PEH("SendEmail", "frmName", ex.Message) 'My error handler


    Finally

        'f.Dispose()
        mailClient.Dispose()
        message.Dispose()


    End Try

在Exchange服务器上，我具有标准的接收连接器组，并且已检查它们是否均按照标准安装进行了配置。我确实尝试创建自己的接收连接器，但是这导致从远程发件人发送的电子邮件出现退回并出现相同的“客户端未通过身份验证”错误，因此我再次将其删除。

任何帮助，将不胜感激。

Graham Sivill。