nanog mailing list archives
Re: Reverse DNS and SMTP
From: Paul Timmins <paul () timmins net>
Date: Thu, 28 Feb 2002 19:29:47 -0500
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:
HiDoes anyone know of a program that can flag such things and alter mail headerson 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. |\ __ /| (`\ | o_o |__ ) ) // \\ Daemon Technologies(tm) | Phone: 510.895.9667 nicole () daemontech com | -------------------(((---(((----------------------- - Powered by FreeBSD - Email, DNS, SiteHosting, FTP Services, Dedicated Servers, Co-Location, and a Lot More ------------------------------------------------------ " Daemons" will now be known as "spiritual guides" -Politically Correct UNIX Page
Current thread:
- Reverse DNS and SMTP Patrick Muldoon (Feb 28)
- RE: Reverse DNS and SMTP Daniel Lark (Feb 28)
- Re: Reverse DNS and SMTP Jared Mauch (Feb 28)
- Re: Reverse DNS and SMTP Nicole Harrington (Feb 28)
- Re: Reverse DNS and SMTP Paul Timmins (Feb 28)
- Re: Reverse DNS and SMTP Chris Adams (Feb 28)
- Re: Reverse DNS and SMTP Jared Mauch (Feb 28)
- RE: Reverse DNS and SMTP Mathias Koerber (Feb 28)
- RE: Reverse DNS and SMTP Daniel Lark (Feb 28)
- <Possible follow-ups>
- RE: Reverse DNS and SMTP Pete Stephenson (Feb 28)
- Re: Reverse DNS and SMTP Conrad A. Rockenhaus (Feb 28)
- Re: Reverse DNS and SMTP David Charlap (Feb 28)