Yes — smtp.web4u.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
smtp.web4u.cz has an AAAA record and answers on it.
✓ 2001:1568::7011 answers · 80
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
2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.
ns.web4u.cz ✓ns2.web4u.cz ✓
yes
HTTPS over IPv6 · not part of the grade yet
smtp.web4u.cz didn't complete an HTTPS request over IPv6 (timed out).
https://smtp.web4u.cz/ via 2001:1568::7011 · timed out
?
 Which outside scripts, fonts, payments or chat smtp.web4u.cz loads from have no IPv6.
 Load smtp.web4u.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/smtp.web4u.cz.svg)](https://aaaa.bot/smtp.web4u.cz)

Check again

smtp.web4u.cz  Has IPv6

A (IPv4)81.91.87.11
AAAA (IPv6)2001:1568::7011

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/PLwTxcwhuu · How we measure

Checked 2026-11-15 17:05:01 UTC. Full DNS report: dns.pizza/domain/smtp.web4u.cz · Age, certificate and blocklists: how.is/smtp.web4u.cz · JSON: /api/v1/smtp.web4u.cz