Mailing List Message #103687
From: Urs Grützner <>
Subject: RDNS (Reverse lookup) failure
Date: Mon, 5 Nov 2012 17:07:40 +0100
To: CommuniGate Pro Discussions <>
X-Mailer: Apple Mail (2.1084)
We have changed our Internet provider, needed to change also the DNS authority and the IP's.

The new zone file on the Master DNS is ok, according to the rules.  

The name Server IPS on the Server are changed to the new provider.

Our server is behind a Firewall, with local IPs,,

The forward and reverse lookup for, and the public IP are OK (see lookups below)

Now we have the following problem:

When sending mails its not the IP of our server which is transmitted, but the IP of our Gateway. Of course the RDNS lookup will fail for servers, which perform this check. 

I do not know how this IP is forwarded with mail. How does the mail server get his own public IP? By checking the DNS?  I don't understand how the gateway IP is coming into the header

Any help is appreciated



PS: Here is a mail I have sent from the concerned server One can see the gateway number as the origin, instead of the mail servers IP number

Von:  Urs Grützner <>

Betreff:  test WAN IP

Datum:  5. November 2012 12:47:33 MEZ

An:  Gruetzner Urs <>

Return-Path:  <>

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„Lookup“ wurde gestartet …

; <<>> DiG 9.6-ESV-R4-P3 <<>> any +multiline +nocomments +nocmd +noquestion +nostats +search
;; global options: +cmd 3600 IN MX 10 3600 IN A
2012103001 ; serial
10800      ; refresh (3 hours)
3600       ; retry (1 hour)
604800     ; expire (1 week)
21600      ; minimum (6 hours)
) 687 IN A 19862 IN A 1833 IN A

„Lookup“ wurde gestartet …

; <<>> DiG 9.6-ESV-R4-P3 <<>> any +multiline +nocomments +nocmd +noquestion +nostats +search
;; global options: +cmd 657 IN A 19832 IN A 1803 IN A

„Lookup“ wurde gestartet …

; <<>> DiG 9.6-ESV-R4-P3 <<>> -x any +multiline +nocomments +nocmd +noquestion +nostats +search
;; global options: +cmd 86400 IN PTR

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