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RBL and Fail-open or closed?

rxjules
Hi,
     I am the domain operator for a network of 25 pc's using Astaro V7.401 and had a question about RBL. For spam control we are only using greylisting and the spam filter. This actually works very well.
     We would like to enable RBL but were concerned if the RBL server(s) do not respond what is the default action of the astaro smtp proxy? Will it reject all incoming emails? Or does it fail-open and allow the emails through. I searched the forums but found no definitive answer to what is the default action.
   Perhaps this could be a feature request if hasn't already been added, I'll have to check.

Thanks for your help,
Julio


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  • 0
    Julio, I remember when one of the RBLs went down, that caused email rejections, so I think it must fail closed.

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • 0 in reply to BAlfson
    Bob, some RBLs have intentionally done things like that to get users to stop using them, so it might not have been Astaro's fault in that case.

    I don't remember how Astaro is configured, but one could point to a random IP as an RBL setting to test it.

    Barry
  • 0 in reply to BarryG
    The default action is accept if there is no response from the rbl. 

    Julio, I remember when one of the RBLs went down, that caused email rejections, so I think it must fail closed.

    The rbl in question is relays.ordb.org. Astaro version 6 was using that by default and was removed here

    By the way, I have been using zen.spamhaus.org for a while and it is rock solid (not too aggressive but catches most). Astaro by default uses sbl-xbl.spamhaus.org and cbl.abuseat.org for spam and pbl.spamhaus.org for dialup lists. zen has sbl, xbl and pbl combined so it cuts down on multiple queries.
  • 0 in reply to Billybob
    Thanks, Billybob, you are correct.

    I just checked to see what I was remembering.  It was the shutdown of the DNS resolution for list.dsbl.org, not the removal of relays.ordb.org.  The problem at the time was that emails were rejected because of the slowness of the response of list.dsbl.org: https://community.sophos.com/products/unified-threat-management/astaroorg/f/56/t/48614

    This was an unusual problem.  If the RBL is down, the email is not blocked.

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
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  • 0 in reply to Billybob
    Thanks, Billybob, you are correct.

    I just checked to see what I was remembering.  It was the shutdown of the DNS resolution for list.dsbl.org, not the removal of relays.ordb.org.  The problem at the time was that emails were rejected because of the slowness of the response of list.dsbl.org: https://community.sophos.com/products/unified-threat-management/astaroorg/f/56/t/48614

    This was an unusual problem.  If the RBL is down, the email is not blocked.

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
Children
  • 0 in reply to BAlfson
    Hi,

    Great thanks for the help. Today I was speaking with an astaro tech about some other issue and when I asked about the RBL they confirmed what others have said. The system will allow emails through if there are problems with responses from RBL's.

    Thanks again, Julio
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