Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
John R Levine <johnl@taugh.com> Sun, 27 September 2020 15:04 UTC
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Date: Sun, 27 Sep 2020 11:04:49 -0400
Message-ID: <9ad77523-9c98-2249-d01c-80ecc6a96fa@taugh.com>
From: John R Levine <johnl@taugh.com>
To: Keith Moore <moore@network-heretics.com>, ietf-smtp@ietf.org
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References: <20200927052221.E0A1A21D3A2D@ary.qy> <198daf90-b3dd-de01-88a0-e9d961feddda@network-heretics.com>
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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On Sun, 27 Sep 2020, Keith Moore wrote: > For example, should the standard insist that client SMTPs have and use an > outgoing IPv4-capable interface any time the server SMTP is reached (directly > or indirectly) via IPv4? Or should client SMTPs be forced to use > IPv6-to-IPv4 SMTP relays rather than NAT64? Should we have to keep > maintaining a public IPv4 network indefinitely (or at least until IPv6 is > globally ubiquitous)? > > To me NAT64 seems like an essential tool for transitioning to IPv6 and one > quite often chosen by carriers, and I don't see the benefit in adding > complexity to the SMTP signal chain (with the consequent degradation of > reliability) just to preserve this rule. This seems backward to me. Keeping in mind that upwards of 90% of all mail is spam, and reliable spam signals are valuable, we know from experience that real mail servers have static addresses and matching forrward and reverse DNS. Anything that comes from a dynamic or NAT pool is invariably spam from a botnet. Small mail servers send and receive on the same address, so if they're going to work on IPv4 at all, they need a static v4 address. Large providers do NAT64 for their customers, but that's not where they put their mail servers (or any servers that need an A record.) They have a chunk of static v4 space for that, and that's where they put their outgoing mail hosts, too. Also remember that mail hosts don't need a lot of address space. I've seen estimates of the total number of SMTP hosts in the 100,000 range. Regards, John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY Please consider the environment before reading this e-mail. https://jl.ly
- [ietf-smtp] EHLO domain validation requirement in… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… John C Klensin
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Russ Allbery
- Re: [ietf-smtp] EHLO domain validation requiremen… John C Klensin
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Ned Freed
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Claus Assmann
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Richard Clayton
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Laura Atkins
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Laura Atkins
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Laura Atkins
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Laura Atkins
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Arnt Gulbrandsen
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Mark Andrews
- Re: [ietf-smtp] EHLO domain validation requiremen… Mark Andrews
- Re: [ietf-smtp] EHLO domain validation requiremen… John R Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Richard Clayton
- Re: [ietf-smtp] EHLO domain validation requiremen… Arnt Gulbrandsen
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Dave Crocker
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Richard Clayton
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… John Levine
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Sam Varshavchik
- Re: [ietf-smtp] EHLO domain validation requiremen… Keith Moore
- Re: [ietf-smtp] EHLO domain validation requiremen… Alessandro Vesely
- Re: [ietf-smtp] own mail server: DNS / static IP … Claus Assmann
- Re: [ietf-smtp] own mail server: DNS / static IP … John Levine
- Re: [ietf-smtp] own mail server: DNS / static IP … Claus Assmann
- Re: [ietf-smtp] own mail server: DNS / static IP … Ned Freed
- Re: [ietf-smtp] own mail server: DNS / static IP … Sam Varshavchik
- Re: [ietf-smtp] own mail server: DNS / static IP … Claus Assmann
- Re: [ietf-smtp] own mail server: DNS / static IP … Arnt Gulbrandsen
- Re: [ietf-smtp] own mail server: DNS / static IP … John Levine
- Re: [ietf-smtp] own mail server: DNS / static IP … John Levine
- Re: [ietf-smtp] own mail server: DNS / static IP … Ned Freed
- Re: [ietf-smtp] own mail server: DNS / static IP … John R Levine
- Re: [ietf-smtp] own mail server: DNS / static IP … Ned Freed
- Re: [ietf-smtp] own mail server: DNS / static IP … Dave Crocker
- Re: [ietf-smtp] own mail server: DNS / static IP … John R Levine
- Re: [ietf-smtp] own mail server: DNS / static IP … Evert Mouw
- Re: [ietf-smtp] own mail server: DNS / static IP … Sam Varshavchik
- Re: [ietf-smtp] own mail server: DNS / static IP … Claus Assmann
- Re: [ietf-smtp] own mail server: DNS / static IP … Laura Atkins
- Re: [ietf-smtp] own mail server: DNS / static IP … Sam Varshavchik