On Sun, Jun 30, 2024 at 06:32:48AM -0600, Dr. Neal Krawetz wrote:
> - Reverse DNS
> If the sender doesn't have a reverse DNS entry, then you can't send email.
> The anti-spam rules also rejects generic reverse hostnames.
> (No "DHCP" or similar in the reverse name.)
> Ah, that's the problem with IPv6 adoption. Almost none have reverse hostnames.
Perhaps you're over-generalising from a personal anecdote, as a
small-scale operator, I for one have not faced any issues with reverse
DNS for IPv6. Presently, my ISP (Aussie Broadband) delegates both a /48
prefix to my router, and its reverse DNS to my DNS server. I have ~2^80
potential IPv6 addresses with FCrDNS to choose from.
> So far, the only mail server I've seen that uses IPv6 with a reverse
> hostname is Google/gmail. That's great for them to send email, but it
> does nothing to permit them to receive email.
Your sample size is too small. Here are a few from my (small) server's
limited logs:
mail-am6eur05olkn20804.outbound.protection.outlook.com[2a01:111:f403:2e12::804]
mail-am6eur05on20700.outbound.protection.outlook.com[2a01:111:f403:2612::700]
[... many more outlook.com ...]
mail-ed1-x52b.google.com[2a00:1450:4864:20::52b]
mail-ed1-x52c.google.com[2a00:1450:4864:20::52c]
[... many more google.com ...]
ant.isi.edu[2001:1878:401::8009:1c09]
cumin.exim.org[2a03:4000:6:b381::2]
digitan.cloud[2a0d:f302:127:b29b::1]
eggs.gnu.org[2001:470:142:3::10]
gal.iecc.com[2001:470:1f07:1126:0:43:6f73:7461]
gitlab.haskell.org[2604:1380:61:2300::1]
ix1.dns-oarc.net[2620:ff:c000::198]
list.sys4.de[2a03:4000:10:51d:b8ce:63ff:feca:a5a0]
mail.NetBSD.org[2001:470:a085:999::25]
mail.gwzoo.com[2a01:8640:5:b::1b9a:3b53]
mail.reichmann.jr-online.org[2001:678:300::90:100:52]
maile-gd.linkedin.com[2620:119:50c0:207::196]
mailman.nlnetlabs.nl[2a04:b900:0:100::25]
misc-services-origin-migration.haskell.org[2604:1380:4641:a100::5]
mta.openssl.org[2600:1900:4060:bf9:0:3::]
mx.mailop.org[2a03:4000:37:599:d8ce:dff:fee1:81c2]
mx0a-00190b01.pphosted.com[2620:100:9001:583::1]
mx2.freebsd.org[2610:1c1:1:606c::19:2]
ra.horus-it.com[2a01:4f9:6a:528d::a]
relay3.msk-ix.ru[2001:6d0:ffff:100::2]
sequoia-grove.ad.secure-endpoints.com[2001:470:1f07:f77:70f5:c082:a96a:5685]
smtp.lax.icann.org[2620:0:2d0:201::1:81]
spike.porcupine.org[2604:8d00:189::2]
--
Viktor.
