who is using require_rdns.m4?

[Alisdair Davey]

On Mon, 2005-06-06 at 13:39, Jeff A. Earickson wrote:
> On Mon, 6 Jun 2005, Michele Neylon :: Blacknight Solutions wrote:
> 
> > Date: Mon, 6 Jun 2005 20:16:32 +0100
> > From: "Michele Neylon :: Blacknight Solutions" <michele at BLACKNIGHT.IE>
> > Reply-To: MailScanner mailing list <MAILSCANNER at JISCMAIL.AC.UK>
> > To: MAILSCANNER at JISCMAIL.AC.UK
> > Subject: Re: who is using require_rdns.m4?
> > 
> > I'd love to do something with this, but I wouldn't like to drop the mail
> > entirely, as I know that there would be a silly amount of valid mail dropped
> > if I did.
> 
> I installed require_rdns.m4 into my sendmail config this morning, and I've
> been watching it closely today.  In approx 6 hours, I've rejected (500 error)
> nearly 2200 emails, with another 1080 tempfails (400 error) for not resolving
> or A/PTR record mismatches.  I've warned our helpdesk about what I did and
> why, and I'm waiting for the yelling to begin.  So far, silence.  The bulk
> of rejections are from APNIC numbers.  I love watching spammers fail.
> 
> >
> > How does it handle shared IPs?
> 
> I've seen machines with multiple NICs and IPs, but never heard of two machines
> sharing the same IP.  Hunh?

I think he is referring to the situation where multiple domain names 
resolve to the same ip, but the ip can only resolve to one name. I would
have thought this is quite common especially among ISPs.
Cheers
Alisdair


> > I was reading somewhere that the reverse and forward records have to match,
> > which would cause issues in some instances
> 
> No reverse DNS = fatal 500 error.  Resolution failures or A/PTR mismatch
> are 400 tempfail errors.  In googling on require_rdns.m4, there is some
> opinion that A/PTR mismatches should be a 500 error too.  I would agree,
> but I'm presently giving mismatches a tempfail error instead.
> 
> Jeff Earickson
> Colby College
> 
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-- 
Dr Alisdair Davey                                 ard at pergamentum.com 
Pergamentum Solutions                             Tel: 1-406-581-6869
2066 Dailey Lane
Superior, CO 80027

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