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Blocking all SMTP requests, except from my smarthost!

FlemmingHougaard

Hi

Situation is as follows:

  • I use the UTM SMTP Proxy functionality in order to use the spamfilter, and attach DKIM-information on ongoing mails!
  • Due to a public address within a DHCP scope, and the fact I can't get my ISP to make an PTR-record, I have to use a smarthost (upstream & downstream) I've created in Azure with postfix.
  • The checkmark "Allow upstream/relay hosts only" is checked, but the SMTP server is still answering on requests - I will get the 550 Access denied (not in relay or upstream list).

What I need:

  • The possibility to create a firewall rule, that will block all incoming SMTP connections.
  • and then a firewall rule, that will allow delivery of mail from my smarthost!

How to do? Can't seem to get it working...

Best regards

Flemming



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Parents
  • "The checkmark "Allow upstream/relay hosts only" is checked, but the SMTP server is still answering on requests - I will get the 550 Access denied (not in relay or upstream list)." I don't understand - can you say that a different way?

    "The possibility to create a firewall rule, that will block all incoming SMTP connections and then a firewall rule, that will allow delivery of mail from my smarthost!" To manage this with any proxy in the UTM, make a NAT rule like 'NoNAT : SmartHost -> SMTP -> External (Address)' and another NAT rule following it like 'DNAT : Internet -> SMTP -> External (Address) : to {unreachable IP}'. To understand better why this is the only solution, see #2 in www.astaro.org/.../49065-rulz.html.

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
Reply
  • "The checkmark "Allow upstream/relay hosts only" is checked, but the SMTP server is still answering on requests - I will get the 550 Access denied (not in relay or upstream list)." I don't understand - can you say that a different way?

    "The possibility to create a firewall rule, that will block all incoming SMTP connections and then a firewall rule, that will allow delivery of mail from my smarthost!" To manage this with any proxy in the UTM, make a NAT rule like 'NoNAT : SmartHost -> SMTP -> External (Address)' and another NAT rule following it like 'DNAT : Internet -> SMTP -> External (Address) : to {unreachable IP}'. To understand better why this is the only solution, see #2 in www.astaro.org/.../49065-rulz.html.

    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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