Yes — mail.master.cz has IPv6.

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

A
IPv6 readiness
Website, mail and DNS all work over IPv6.
Website over IPv6
mail.master.cz has an AAAA record and answers on it.
✓ 2a01:430:100:5c::2 answers · 443
yes
Mail servers (MX) have IPv6
No MX records, so mail goes to the domain's own address (implicit MX). It has an AAAA record.		yes
Nameservers have IPv6
3 of 3 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.
ns1.master.cz ✓ns2.master.cz ✓ns3.master.cz ✓
yes
HTTPS over IPv6 · not part of the grade yet
Loads over IPv6 with a valid certificate: HTTP 200.
https://mail.master.cz/ via 2a01:430:100:5c::2 → 200
works
 Load mail.master.cz over IPv6 from up to six other places — a second opinion.

Nothing keeping you from an A

  1. Nothing to fix
    Show it off: add the badge to your README.
    [![IPv6](https://aaaa.bot/badge/mail.master.cz.svg)](https://aaaa.bot/mail.master.cz)

Check again

mail.master.cz  Has IPv6

A (IPv4)81.31.43.64
AAAA (IPv6)2a01:430:100:5c::2

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

 Permanent link: aaaa.bot/r/I0MbXKUNWY · How we measure

Checked 2026-11-05 16:06:58 UTC. Full DNS report: dns.pizza/domain/mail.master.cz · Age, certificate and blocklists: how.is/mail.master.cz · JSON: /api/v1/mail.master.cz