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Thread: Sending Mail not working

  1. #1
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    Default Sending Mail not working

    I am getting lot of return unknow delivery messages from other email servers
    due to a spam from our Zimbra version zcs-5.0.1_GA. I don't know how they were able to break in Zimbra and do that. In any case, at this point I would like to use the function that exit within Zimbra to prevent some of these spam
    and Here is my question:


    1.
    I want to stop email from sending out for this particular user.
    So I went through this process and it did not work. I have turn off
    the check box and tested and it still allow the user to sending out email.


    In Administration Console,
    Under Manage Accounts, Preferences, Sending Mail section.


    There is a check box for Allow Sending Email from any address.
    I unchecked it and have not thing under this line
    Allow sending email only from these addresses:

    This particular user stilled able to sending out email.


    I have also tried with admin@localdomain.com for this line
    Allow sending email only from these addresses:


    And the use was still able to sending out email.



    2.
    What/Where are the commands or how can I verify the SMTP RELAY for Pop3/Imap are set up correctly?



    Thank you in advance,


    Yoom

  2. #2
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    Are you sure they were sent from your server ? It is very easy to spoof one of your email address, and you will get the backscatter from the other email servers.

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    Quote Originally Posted by yoom@hostwebase.com View Post
    What/Where are the commands or how can I verify the SMTP RELAY for Pop3/Imap are set up correctly?
    Hi Yoom,

    I'm not sure if you mean verifying whether your server is allowing SMTP relay from external sites or not - if so, you can go to sites like SpamHelp.org SMTP Open Relay Test and enter your server's address there. It will inform you if your server allows SMTP relay or not. By default it shouldn't though.

    As uxbod said, it's very easy for spammers to send bulk emails out from their own servers and set the sender address as someone from your domain - my personal mail server has been flooded by this recently in fact, and it's a real pain as you start receiving hundreds of delivery failures, etc for mails that never originated from your site.

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    You could install the SendMail nullmail milter into Postfix which would stop a lot of the bounces. Greylisting would also help in this situation.

  5. #5
    phoenix is offline Zimbra Consultant & Moderator
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    Quote Originally Posted by yoom@hostwebase.com View Post
    I am getting lot of return unknow delivery messages from other email servers
    due to a spam from our Zimbra version zcs-5.0.1_GA. I don't know how they were able to break in Zimbra and do that.
    Nobody has .broken into' your Zimbre server. This is commonly known as backscatter spam, search the web for further details, you can also search the forums for a thread or two on how to resolve the problem.
    Regards


    Bill


    Acompli: A new adventure for Co-Founder KevinH.

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    Default Unsure-perhaps problem with backsscatter

    Quote Originally Posted by uxbod View Post
    Are you sure they were sent from your server ? It is very easy to spoof one of your email address, and you will get the backscatter from the other email servers.


    Uxbod,


    I am definetely not sure. I know that we get so much of delivery failures.
    It sounds like what you have described BACKSCATTER.
    It make sense. Now, I need find a fix for it.

    Thank you so much for respond to my question.

    Yoom

  7. #7
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    MBD,


    Yes, We have receiving hundreds of delivery failures. Did you fix the problem?
    Is there something I should know from your learning and experience in fixing the problem?


    Regarding SMTP relay for pop3:
    My question was more for how to define or allow an external domain or
    an external IP address to use our server as a SMTP RELAY for their pop3
    account. The GUI console doesn't seem to work
    if I recalled. I am looking for some example via command lines.


    Thank you so much for respond to my question.

    Yoom

  8. #8
    phoenix is offline Zimbra Consultant & Moderator
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    Quote Originally Posted by yoom@hostwebase.com View Post
    MBD,


    Yes, We have receiving hundreds of delivery failures. Did you fix the problem?
    Is there something I should know from your learning and experience in fixing the problem?
    Search the forums for the answer to backscatter spam, there's a recent thread that describes a fix for it.
    Regards


    Bill


    Acompli: A new adventure for Co-Founder KevinH.

  9. #9
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    Just posted http://www.zimbra.com/forums/adminis...ckscatter.html on another thread so here ya go

  10. #10
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    Quote Originally Posted by phoenix View Post
    Search the forums for the answer to backscatter spam, there's a recent thread that describes a fix for it.


    Phoenix,

    I found this old respond from you.
    If I have more than one domain being spam then I list as the following?

    whitelist_bounce_relays domain1.com domain2.com domain3.com

    or

    whitelist_bounce_relays domain1.com
    whitelist_bounce_relays domain2.com
    whitelist_bounce_relays domain3.com


    Also, is this the only file I have to modify (local.cf) ?

    Thank you.

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