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Forwarding Relay and Exchange

Posted: 2008-11-24 07:03
by porcupine
Hi Guys,

this is not a question or problem, just something that was observed today when Spamhaus changed a policy it uncovered an error in our setup.

We use hMail as a SMTP gateway for our Exchange server and also keep some domains on it that we don't need the Exchange features for.

- hMail is set to check Exchange for Spam (set in the IP Ranges)
  • When hMail is set to check for Spam it will verify the sending IP against our Spam policy (SpamCop, Spamhaus etc).
- hMail is set to treat Exchange as a Forwarding Relay (set in the IP Ranges)
  • When hMail is set to treat as a Forwarding Relay it will bypass the server’s IP and check the SMTP headers
  • When Exchange routes email to hMail there is no IP in the SMTP headers so hMail uses
- at 7.45am Spamhaus changes their response policy
  • at 7.45:18am and earlier results with 0 (not Spam)
    at 7.45:47am results with 1 (Spam)
    • "TCPIP" 2676 "2008-11-24 07:45:18.645" "DNSResolver - INAddr Lookup result for 0 responses"
      "TCPIP" 4004 "2008-11-24 07:45:47.006" "DNSResolver - INAddr Lookup result for 1 responses"

      We obviously didn't need to check for Spam and didn't fully understand what Forwarding Relay meant. Even on our backup MX there is no need for the Forwarding Relay setting because it is also hMail as it has the same Spam Protection as the primary.

      Forwarding Relay is intended to be used when your backup MX (or other relay) does not have adequate Spam protection, which is fine:- ... ce_iprange