Date: Wed, 15 Apr 1998 11:31:14 +0930 From: Greg Lehey <grog@lemis.com> To: Dan Busarow <dan@dpcsys.com> Cc: Jeff & Hillary Jones <kf7nn@mutsgo.dyn.ml.org>, questions@FreeBSD.ORG Subject: Re: domain resolve for email Message-ID: <19980415113114.R1870@freebie.lemis.com> In-Reply-To: <Pine.BSF.3.96.980414104216.3526O-100000@java.dpcsys.com>; from Dan Busarow on Tue, Apr 14, 1998 at 10:49:30AM -0700 References: <19980414164844.I1870@freebie.lemis.com> <Pine.BSF.3.96.980414104216.3526O-100000@java.dpcsys.com>
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On Tue, 14 April 1998 at 10:49:30 -0700, Dan Busarow wrote:
> On Tue, 14 Apr 1998, Greg Lehey wrote:
>> Jeff Jones wrote:
>>> I would like to know how to make it so my email accounts
>>> do not get mail from unresolveable hosts just like
>>> this list.
>>
>> I'm no longer sure that this is a good idea. Over the last couple of
>> days I have set up a mailing list, and I find that a large number of
>> legitimate users have transient problems in their reverse lookup (not
>> their fault, nor of anybody in their domain). The result is that mail
>> to or from them bounces. I've taken mine out as a result.
>
> The "standard" rule for this returns a temporary error so transient
> problems shouldn't do more than slow mail from them down.
>
> Here's the one we use
>
> Scheck_mail
> # verify valid DNS entry
> R$* $: <?> $>3 $1
> R<?> $* < @ $+ . > $: <OK>
> R<?> $* < @ $+ > $#error $: 451 Domain must resolve $1@$2 $&{client_addr}
>
> I go through the logs checking these once or twice a month. Catches
> a huge amount of spam and I've only seen one instance where a legit address
> was refused. YMMV
This is exactly the rule I had. Yes, it's a 4xx error number, but a
surprising number of mailers give up when they see it. I haven't
investigated why.
I've had a large number of problems with reverse lookup in the last
week. In particular, the IP address of my PPP link to the outside
world keeps dropping off the net. This seems to be related to one
particular name server, munnari.oz.au, but it's taking its time to be
fixed.
Greg
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