External mail being returned

Discussion in 'Windows Small Business Server' started by John, Nov 5, 2004.

  1. John

    John Guest

    Hi

    Whenever a user sends a mail to an external email, he/she gets the following
    message;

    The following recipient(s) could not be reached:
    on ...
    You do not have permission to send to this recipient. For assistance,
    contact your system administrator.
    <mydomain.com #5.7.1>

    The problem started when the client were informed by their isp that their
    server was being used to relay thousands of spam emails. They in their hurry
    to stop spam relay, did a few changes based on what they were told over the
    phone by isp tech support. This stopped the spam but also all external
    emails. They can't remember all the things they did.

    I have gone through the server and checked and corrected the common things
    like recipient policies & SMTP virtual server. The external mail has still
    not worked. Is there another place that I need to look at? Also what is the
    way to avoid the server being used as an open relay?

    Thanks

    Regards
     
    John, Nov 5, 2004
    #1
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  2. John

    Henry Craven Guest

    How did they manage to configure the server as an open relay in the
    first place ? ( considering it's locked down by default.... )

    Have you re-run the CEICWizard and if you're using Smart-host set the
    correct authentication ?
     
    Henry Craven, Nov 5, 2004
    #2
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  3. John

    John Guest

    Re-ran the wizard a couple of time. No luck. Not sure if I am running
    smart-host. How do I check?

    Regards
     
    John, Nov 6, 2004
    #3
  4. See http://www.vamsoft.com/orf/authattack.asp

    If you don't have strong/complex password policies enabled, force regular
    password changes, have enabled guest, etc., someone may exploit
    authenticated relay. If you don't need authenticated relay, disable it. You
    can always have any external POP users use their own ISP's SMTP server for
    outbound mail anyway.
     
    Lanwench [MVP - Exchange], Nov 6, 2004
    #4
  5. John

    Henry Craven Guest

    Perhaps that should have been *Dis-able* guest.

    ....but I agree if someone can dictionary hack your admin user and
    passwords... well.....

    --
    Henry Craven {SBS-MVP}
    Melbourne Australia


    "Lanwench [MVP - Exchange]"
     
    Henry Craven, Nov 6, 2004
    #5
  6. John

    John Guest

    No external email is currently going out so it is completely safe at the
    moment. :) How do I get some external mail going?

    Thanks

    Regards


    "Lanwench [MVP - Exchange]"
     
    John, Nov 6, 2004
    #6
  7. John

    Henry Craven Guest

    Re-run the CEICWizard and either configure the DNS SMTP or Smarthost.
    ( Check if the ISP Changed the Logon/Authentication details for
    Smarthost first if you're using it. )

    Also check if the client has been Blacklisted as an open relay on the OR
    Blocker weblists and begin processes to have them removed ( ....that
    may take a week or so ).
     
    Henry Craven, Nov 6, 2004
    #7
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