mail.knight-networks.com is hosted in AWS and has IPv6 rDNS.
When I first set up the mail server in 2018, it was a manual process for
them to configure it. It's since moved to an automated process to
request it.
Fwiw, to address another part of the thread, I regularly send SMTP to
Gmail users over IPv6 with no issues.
-Brian
$ host mail.knight-networks.com
mail.knight-networks.com has address 18.217.5.117
mail.knight-networks.com has IPv6 address
2600:1f16:b15:6902:ad0e:540b:da86:d1eb
$ host 2600:1f16:b15:6902:ad0e:540b:da86:d1eb
b.e.1.d.6.8.a.d.b.0.4.5.e.0.d.a.2.0.9.6.5.1.b.0.6.1.f.1.0.0.6.2.ip6.arpa
domain name pointer mail.knight-networks.com.
$ whois 2600:1f16:b15:6902:ad0e:540b:da86:d1eb
[snip]
NetRange: 2600:1F00:: - 2600:1FFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF
CIDR: 2600:1F00::/24
NetName: AMZ-EC2
NetHandle: NET6-2600-1F00-1
Parent: NET6-2600 (NET6-2600-1)
NetType: Direct Allocation
OriginAS:
Organization: Amazon.com, Inc. (AMAZO-4)
RegDate: 2014-10-17
Updated: 2014-10-17
[snipcert]
Ref: https://rdap.arin.net/registry/ip/2600:1F00::
OrgName: Amazon.com, Inc.
OrgId: AMAZO-4
Address: Amazon Web Services, Inc.
Address: P.O. Box 81226
City: Seattle
StateProv: WA
PostalCode: 98108-1226
Country: US
RegDate: 2005-09-29
Updated: 2022-09-30
Comment: For details of this service please see
Comment: http://ec2.amazonaws.com
Ref: https://rdap.arin.net/registry/entity/AMAZO-4
[snip]
On 2026-01-01 17:48, John R Levine via mailop wrote:
Are you sure your ipv6 ptr is set as well?
For providers that offer IPv6, you're right, you need to be able to set
your IPv6 rDNS, which rules out AWS. Fortuantely there are other
providers where that works.
R's,
John
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