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Tarpit in Exchange 2010

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  • Tarpit in Exchange 2010

    Hello,

    We are using Exchange 2010 and we have set the tarpit interval, for all three receive connectors we are using, to 20 seconds. When I try to send a mail to a non-existent address I get a NDR directly, it doesnīt wait the 20 seconds before it sends the NDR. What can be wrong?

    Regards,
    stroba

  • #2
    Re: Tarpit in Exchange 2010

    Tarpitting not the delay of sending a NDR. It's pausing respons after a threshold of errors (like trying to send to non-existent addresses) has been reached from the same source server.

    Example: servers send to non-existent address. Does that 3 times and very quickly. After that, your Exchange server pauses 20seconds after every request (have to look what exactly etc.) from that very same server. Now sending to a non-existing mail the fourth time adds at least 20 seconds to the whole process. Idem with the fifth etc. etc..This way bulk mailing or email harvesting becomes slow, more expensive and thus less attractive.

    Just to be sure: Have you restarted the Transport Service after changing values?

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    • #3
      Re: Tarpit in Exchange 2010

      Ok, I thought tarpitting affected all emails. Do you know where I can find some documentation on how this works? I havenīt found anything saying there is a threshold that has to be reached...

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      • #4
        Re: Tarpit in Exchange 2010

        Originally posted by stroba View Post
        Ok, I thought tarpitting affected all emails. Do you know where I can find some documentation on how this works? I havenīt found anything saying there is a threshold that has to be reached...
        I believe the maximum tarpit time that can be set is 10 minutes. But there's generally no need to modify the 5 second default interval unless you're experiencing some type of bulk email or directory harvest issue. The purpose of the tarpit being to lengthen the smtp transaction\conversation on internet facing servers if your server see's spurious activity coming from an internet mail server. Can you provide some context on 'why' you'd like to increase this time from the default?

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        • #5
          Re: Tarpit in Exchange 2010

          Originally posted by stroba View Post
          Ok, I thought tarpitting affected all emails. Do you know where I can find some documentation on how this works? I havenīt found anything saying there is a threshold that has to be reached...
          Here are some helpfull links:
          Understanding Recipient Filtering > Tarpitting Functionality
          Set-ReceiveConnector

          I thought there was a threshold, but as I read the text now it is the "550 5.1.1 User unknown" response that is delayed. The maximum interval is indeed 10 minutes.

          I agree with scurlarunting BTW, what is your goal?

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