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Re: [DNSOP] Review of draft-livingood-dns-redirect-00

Tony Finch <dot@dotat.at> Mon, 13 July 2009 11:21 UTC

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Date: Mon, 13 Jul 2009 12:21:44 +0100
From: Tony Finch <dot@dotat.at>
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To: Florian Weimer <fw@deneb.enyo.de>
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References: <C67B83C4.E855%Jason_Livingood@cable.comcast.com> <87ws6enw09.fsf@mid.deneb.enyo.de> <74DA3552-160F-4912-B8B4-FAD506B4D4D1@eng.colt.net> <4A5AEA32.5010102@NLnetLabs.nl> <87tz1hyokg.fsf@mid.deneb.enyo.de>
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Cc: dnsop@ietf.org, "Livingood, Jason" <Jason_Livingood@cable.comcast.com>, Jelte Jansen <jelte@NLnetLabs.nl>
Subject: Re: [DNSOP] Review of draft-livingood-dns-redirect-00
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On Mon, 13 Jul 2009, Florian Weimer wrote:
> * Jelte Jansen:
> >
> > then a SERVFAIL will also result in an e-mail bounce that says
> > connection refused
>
> Not a hard 5xx error?

No, both SERVFAIL and connection refused are equivalent to 4yz temporary
failures.

> > instead of DNS error (assuming there's no e-mail
> > sink on the host that is redirected to). Fun times for the helpdesk.
>
> Only if the mail server falls back to the A record if the MX lookup
> results in SERVFAIL, which seems like a questionable approach to me.

Yes, it would be wrong to do that.

> Anyway, I think DNS rewriting is mainly for folks who also block
> 25/TCP in- and outgoing or list the address space on the PBL and
> similar DNSBLs, so the SMTP argument is not really valid anymore.

The draft should probably say something like that explicitly.

However there's an unbounded number of similar problematic examples: what
if the user is running an XMPP server?

RFC 4084 is probably relevant.

Tony.
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