Re: 3rd party spam filter and virtual users

From: John Evans (no email)
Date: Tue May 15 2007 - 13:30:01 EDT

  • Next message: Noel Jones: "Re: Email routing like MX functionality"

    On Tue, 15 May 2007, Lars Johansen wrote:

    > Hi we have a setup with postfixadmin and virtual users.. everything
    > works great, but we have one issue.
    > We want to use a 3rd party spam service provider.. but we dont want to
    > set our MX records to them..

    I work for one of those "third party spam service providers" (no, I can't
    which one, sorry.)

    If you receive all of your email, forward it to a 3rd party, ask them to
    filter it, and send legitimate mail back to you, you're going to be
    blowing a huge amount of bandwidth. You'll be sending spam messages
    through your pipe at least twice, and legitimate mail through at least
    three times. Not a good idea.

    Also, most third part spam service providers use some form of IP
    reputation schema. This means that you will be sending all of your mail
    flow (including spam) to them, and this will poison their IP reputation
    database AGAINST you. This means that they will start to consider all
    messages that come from you as spam, and this will skew their results. In
    the end, they will most likely start blocking legitimate mail just based
    on the reputation of your IP address.

    > The thing we want is to be able to filter all mail that does not come
    > from this 3rd party.. and redirect it to them..

    If you don't redirect your MX record to the third party, how will email
    destined for your domain(s) ever reach the third party in the first place
    unless you send it to them? Because you don't want to change your MX
    record to point to the third party, there is zero chance that they will
    get your email in the first place. This means that 100% of your mail from
    come from the original sender (or open relay in the case of most spam),
    not from the third party.

    Do the smart thing. Change your MX record to the third party, and allow
    them to do what you are paying them to do for you. It will save your
    bandwidth, CPU cycles, disk storage, and will make your users happier in
    the end.

    John Evans
    Administrator of

  • Next message: Noel Jones: "Re: Email routing like MX functionality"

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