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Thread: postfix username check

  1. #1
    Join Date
    Nov 2005
    Rep Power

    Default postfix username check


    Can I know how to prevent postfix to deliver mails that use a non-valid username that are from the same domain?

    Example: our domain is and does not exist in our domain. But would a bad spammer able to use to send emails to internal users? Any way to stop that? OR is that a default feature in zimbra to block that?



  2. #2
    Join Date
    Oct 2005
    Thatcher, AZ
    Rep Power


    If the account doesn't exist in the domain, then a spammer will not be able to send messages to an account that doesn't exist.

    A good way to check to see how effective your spam protection is, is to do an open-relay test.

    During most open relay tests, the test tries to do exactly what you're saying, and shows you the results/output.

    When I was testing out an e-mail server for my school, I went through several ones. One feature of zimbra is that it blocks open relay.

    Open Relay Test Here <-HIGHLY Reccommended!
    DNS Stuff's Mail Test

    Good luck. Try the test. If this doesn't solve the problem, please follow up.
    Last edited by jholder; 05-17-2006 at 09:03 PM.

  3. #3
    phoenix is offline Zimbra Consultant & Moderator
    Join Date
    Sep 2005
    Vannes, France
    Rep Power


    Quote Originally Posted by achow
    Any way to stop that? OR is that a default feature in zimbra to block that?
    It's the default nature of Postfix (and hence Zimbra) to not allow that sort of behaviour by default. The only 'gotcha' is if you have added a catch-all address which will get all the mail addressed to non-existent users. You should also run the relay tests that wannabetenor has given you the links for, just to make sure.


    Acompli: A new adventure for Co-Founder KevinH.

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