mail.census.gov publishes IPv6 but doesn't answer on it.

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

F
IPv6 readiness
Publishes IPv6 but doesn't answer on it — worse than having none.
Website over IPv6
mail.census.gov has an AAAA record, but nothing answered on ports 443 or 80. IPv6 visitors wait for a timeout before falling back to IPv4.
✗ 2610:20:2000:101::f:0 no answer✗ 2610:20:2010:a04::f:0 no answer
broken
Mail servers (MX) have IPv6
Every mail server has an AAAA record.
mail1.census.gov ✓mail2.census.gov ✓
yes
Nameservers have IPv6
2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.
ns1e.census.gov ✓ns2e.census.gov ✓
yes
 Load mail.census.gov over IPv6 from up to six other places — a second opinion.

What's keeping mail.census.gov from an A

  1. Fix or remove the AAAA record for mail.census.gov
    Something published an IPv6 address but nothing answers on it, so IPv6 visitors wait for a timeout first. Either make the server listen on IPv6 (and allow ports 443/80 through its firewall), or delete the AAAA record until it does.

Check again

mail.census.gov  Has IPv6

A (IPv4)148.129.75.15
148.129.129.15
AAAA (IPv6)2610:20:2000:101::f:0
2610:20:2010:a04::f:0

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/ZsWOHZ5A9S · How we measure

Checked 2026-11-01 20:12:52 UTC. Full DNS report: dns.pizza/domain/mail.census.gov · JSON: /api/v1/mail.census.gov