http://www.spambouncer.org I have no connection to this software other than being a satisfied user. -Paul At 07:29 PM 2/28/2002, Nicole Harrington wrote:
Hi Does anyone know of a program that can flag such things and alter mail headers on the fly like this?
Nicole
On 28-Feb-02 Unnamed Administration sources reported Jared Mauch said :
On Thu, Feb 28, 2002 at 01:35:09PM -0700, Daniel Lark wrote:
You are most correct, it is definitely a double edged sword. Let's say you try to reverse DNS on an address who's nameserver is down or otherwise unreachable, what then? Some admins I know deliberately do run reverse DNS as they view it as system cracker tool, or they feel it is an unwarranted load, RFCs be damned. Is this admin decision the fault of the user?
Use a non clueless isp. the market is fairly saturated in most places with service providers.
You are not first one to try this. I have tried this myself and a financial type didn't get an important email because of it. You know the rest of the story.
What I do is format my smtp headers such that a very simple regex can find mail with no reverse dns and dump it in a spam folder. I find this catches a lot of the messages.
I try and let people know but for example, I am unable to find anyone at American Express or NWA that can fix their dns. (others are prompt in fixing their dns problems).
A better solution is to check the ip and see if it is an MX record for the domain the mail purports to be from.
This has a number of flaws. I won't delve into them though.
Just my opinion, and I could wrong.
- Jared
-dan
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Patrick Muldoon Sent: Thursday, February 28, 2002 1:15 PM To: nanog@merit.edu Subject: Reverse DNS and SMTP
We have recently implemented a policy on our mail servers of not accepting mail from hosts that do not correctly resolve via reverse DNS. While we on the technical side love the idea, there have been some questions from the business side of the house.
If an ISP who doesn't have reverse DNS setup correctly on their mail servers, we point them to the RFC's and generally offer to help them correct it. We have noticed that our spam has reduced drastically, and the complaints are few, but alas this is a double edged sword, where if you even block 1 legitimate e-mail out of the 100K+ that we receive daily, someone is going to complain.
Just curious if anybody here is doing the same and the response that they have had from doing so. Replies off list are fine and I will summarize if people are interested.
Thanks, Patrick
-- Patrick Muldoon, Network/Software Engineer INOC, LLC doon@inoc.net
Press Ctrl-Alt-Del now for IQ test.
-- Jared Mauch | pgp key available via finger from jared@puck.nether.net clue++; | http://puck.nether.net/~jared/ My statements are only mine.
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