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Completely Block Mail from Internal Domain

For our Company Domain (petroleumtraders.com) all our users send emails from Inside the firewall. So we know any email that comes from outside the firewall with that as a sending address is fake. So we have a *@petroleumtraders.com Address pattern added to the Sender BlackList section of the AntiSpam tab on our email protection. 

But today one of our Vice Presidents got a fake email that appeared to be from the owners address complete with a @petroleumtraders.com address. Luckily it looked a little suspicious because it was a wire transfer request.

After inspecting the email I found in the header that the X-Sender was a external address and the From header was a @petroleumtraders.com and the Reply-To, Return-Path were also a external address. 

So I guess the Sender blacklist does not block the "envelope-from" address?

How can I block these so internal users can't be tricked?

Dan


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Parents
  • Great idea to think about his problem instead of how to make his solution work like the rest of us! SPF is easy and also should be done, but I think it would not prevent Dan's problem.  Rather, it would be DKIM he wants.  I see someone copied my instructions for setting this up, so rather than offering to send you each a copy, here's the link to the KnowledgeBase article.

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
Reply
  • Great idea to think about his problem instead of how to make his solution work like the rest of us! SPF is easy and also should be done, but I think it would not prevent Dan's problem.  Rather, it would be DKIM he wants.  I see someone copied my instructions for setting this up, so rather than offering to send you each a copy, here's the link to the KnowledgeBase article.

    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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