Security Basics mailing list archives

Re: educating rDNS violators


From: Derek Schaible <dschaible () cssiinc com>
Date: Wed, 25 Aug 2004 07:00:35 -0400

On Mon, 2004-08-23 at 15:24, JGrimshaw () ASAP com wrote:
I was under the impression that reverse DNS for the Internet was 
essentially broken, due to several large ISPs not necessarily implementing 
reverse DNS for their many subnetted customers. 

I have the (mis)fortune of being a customer of a large ISP who resells a
portion of a class C to us. As with most customers in this situation I
run my own DNS with no authority over my reverse DNS. But if you call
your ISP's help line and ask them to correct your reverse DNS entry for
your mail servers they more than likely will be ecstatic to help you
out.

Personally, I can say my spam reduced over 85% by dropping mail that
doesn't come from a server with correct reverse DNS information. All
ISP's want to see spam reduced and if your ISP won't assist you in
correcting your reverse info, I'd be shopping for a new ISP.

Hope this helps someone out!

-- 
Derek Schaible <dschaible () cssiinc com>
CSSI, Inc.

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