Yes — benu.cz has IPv6.

Has both IPv4 (A) and IPv6 (AAAA) addresses.

IPv6 readiness

Works over IPv6, with one gap: its mail servers lack IPv6.

Website over IPv6 benu.cz has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:10::6814:2279 answers · 443✓ 2606:4700:10::ac42:9608 answers · 443	yes
www over IPv6 www.benu.cz has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:10::6814:2279 answers · 443✓ 2606:4700:10::ac42:9608 answers · 443	yes
Mail servers (MX) have IPv6 None of the mail servers has an AAAA record. mail01.phoenixgroup.eu ✗mail02.phoenixgroup.eu ✗mail03.phoenixgroup.eu ✗mail04.phoenixgroup.eu ✗	no
Nameservers have IPv6 2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up. hunts.ns.cloudflare.com ✓joyce.ns.cloudflare.com ✓	yes

HTTPS over IPv6 · not part of the grade yet
Loads over IPv6 with a valid certificate after 1 redirect: HTTP 403.

https://benu.cz/ via 2606:4700:10::6814:2279 → 307https://www.benu.cz/ via 2606:4700:10::6814:2279 → 403

works

What's keeping benu.cz from an A

Mail servers without IPv6
mail01.phoenixgroup.eu, mail02.phoenixgroup.eu, mail03.phoenixgroup.eu, mail04.phoenixgroup.eu have no AAAA record, so mail from IPv6-only servers can't reach them directly. If a provider runs your mail, that's their setting; if you run it, add AAAA records for these hosts.

Check again

benu.cz Has IPv6

A (IPv4)	104.20.34.121 172.66.150.8
AAAA (IPv6)	2606:4700:10::6814:2279 2606:4700:10::ac42:9608

www.benu.cz Has IPv6

A (IPv4)	104.20.34.121 172.66.150.8
AAAA (IPv6)	2606:4700:10::6814:2279 2606:4700:10::ac42:9608

Browsers on dual-stack networks will usually pick IPv6 here (the "Happy Eyeballs" algorithm races both and prefers v6).

Copy the evidence — a citation-ready record of this measurement

IPv6 measurement: benu.cz
Measured 2026-11-05 16:47:59 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    104.20.34.121, 172.66.150.8
AAAA (IPv6): 2606:4700:10::6814:2279, 2606:4700:10::ac42:9608
www AAAA:    2606:4700:10::6814:2279, 2606:4700:10::ac42:9608

Readiness grade B: Works over IPv6, with one gap: its mail servers lack IPv6.
- Website over IPv6: benu.cz has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:10::6814:2279: answers (TCP 443)
    2606:4700:10::ac42:9608: answers (TCP 443)
- www over IPv6: www.benu.cz has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:10::6814:2279: answers (TCP 443)
    2606:4700:10::ac42:9608: answers (TCP 443)
- Mail servers (MX) have IPv6: None of the mail servers has an AAAA record.
- Nameservers have IPv6: 2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.

Reachability = a TCP connection opened on port 443 (or 80).

HTTPS over IPv6 (not graded): Loads over IPv6 with a valid certificate after 1 redirect: HTTP 403.
    https://benu.cz/ via 2606:4700:10::6814:2279 -> HTTP 307, certificate: valid
    https://www.benu.cz/ via 2606:4700:10::6814:2279 -> HTTP 403, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/iO3oErc46y

Permanent link: aaaa.bot/r/iO3oErc46y · How we measure

Checked 2026-11-05 16:47:59 UTC. Full DNS report: dns.pizza/domain/benu.cz · Age, certificate and blocklists: how.is/benu.cz · JSON: /api/v1/benu.cz