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Reverse DNS Lookup problem

Printed From: LogSat Software
Category: Spam Filter ISP
Forum Name: Spam Filter ISP Support
Forum Description: General support for Spam Filter ISP
Printed Date: 26 September 2018 at 4:33am

Topic: Reverse DNS Lookup problem
Posted By: Guests
Subject: Reverse DNS Lookup problem
Date Posted: 18 May 2003 at 8:21am

Hi there

I have recently installed Spamfilter. My mailserver and spamfilter is on the same server behind a NAT-router/firewall.

The problems is the DNS lookup, as it tries to lookup the LAN IP ( of my router. Therefore any emails will naturally be rejected.

Now if I disable Reverse DNS lookup, spamfilter hardly catches any spammails. It still does MAPS lookup though.

What can I do?

(sorry for my lousy english)

Posted By: Guests
Date Posted: 18 May 2003 at 9:09am
If you have DNS running on a server behind your firewall you could create a reverse zone for your private dns.

Posted By: Guests
Date Posted: 18 May 2003 at 9:10am
If no DNS server you could put an entry in your HOSTS file on the server that SpamFiler is running on.

Posted By: Guests
Date Posted: 18 May 2003 at 9:38am
I see your point, but is it really necessary to for Spamfilter to lookup DNS in order to work?

Posted By: LogSat
Date Posted: 18 May 2003 at 9:53am


In order to function with the most capabilities, SpamFilter must be able to *see* the real IP of the remote server connecting to your network. It is based on the sender's IP address that SpamFilter can lookup that IP in the blacklists, see what country it's from, check if it has a reverse DNS and more.

If I understood you correctly, during the DNS lookup of an incoming connection SpamFilter is trying to resolve your address. If this is so, it means that your router/firewall is accepting the incoming connection, but it then provides SpamFilter with a translated address of, not the original IP. Without that original IP, SpamFilter's functionality is severily crippled...

If I correctly understood your configuration, you will need to configure your firewall so that it provides SpamFilter with the true IP address of the sender.

Roberto Franceschetti
LogSat Software

Posted By: Guests
Date Posted: 18 May 2003 at 9:56am

Thanks for your very quick answer.

So the conclusion is that Spamfilter doesn't work with NAT routers?

Posted By: Guests
Date Posted: 18 May 2003 at 10:03am

Sorry....forget that last post.

It was only a matter of configuring my firewall correctly. It was configured for masquerading on the private interface.

Thanks for you support :-)

Posted By: LogSat
Date Posted: 18 May 2003 at 10:06am

Glad it worked! I would not have been able to help on the firewall side. The ones I've dealt with allow that to be done in a way or another, but they're all different...

LogSat Software

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