Yes — letterline.app has IPv6.

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

IPv6 readiness

Website, mail and DNS all work over IPv6.

Website over IPv6 letterline.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2a02:4780:84:139c:3ce2:aff2:f0a3:2752 answers · 443✓ 2a02:4780:84:e624:23e1:f476:5971:3dbc answers · 443	yes
www over IPv6 www.letterline.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2a02:4780:84:b6c2:a21d:5cff:ef30:6fa3 answers · 443✓ 2a02:4780:84:cb37:dd6f:156a:2ff4:45f6 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 2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up. cosmos.dns-parking.com ✓nova.dns-parking.com ✓	yes

HTTPS over IPv6 · not part of the grade yet
Loads over IPv6 with a valid certificate: HTTP 200.

https://letterline.app/ via 2a02:4780:84:139c:3ce2:aff2:f0a3:2752 → 200

works

Nothing keeping you from an A

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

Check again

letterline.app Has IPv6

A (IPv4)	84.32.84.64 2.57.91.254
AAAA (IPv6)	2a02:4780:84:139c:3ce2:aff2:f0a3:2752 2a02:4780:84:e624:23e1:f476:5971:3dbc

www.letterline.app Has IPv6

Alias of	www.letterline.app.cdn.hstgr.net
A (IPv4)	191.96.144.25 212.1.212.211
AAAA (IPv6)	2a02:4780:84:b6c2:a21d:5cff:ef30:6fa3 2a02:4780:84:cb37:dd6f:156a:2ff4:45f6

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: letterline.app
Measured 2026-11-05 14:44:01 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    84.32.84.64, 2.57.91.254
AAAA (IPv6): 2a02:4780:84:139c:3ce2:aff2:f0a3:2752, 2a02:4780:84:e624:23e1:f476:5971:3dbc
www AAAA:    2a02:4780:84:b6c2:a21d:5cff:ef30:6fa3, 2a02:4780:84:cb37:dd6f:156a:2ff4:45f6

Readiness grade A: Website, mail and DNS all work over IPv6.
- Website over IPv6: letterline.app has 2 IPv6 addresses and answers on every one we tested.
    2a02:4780:84:139c:3ce2:aff2:f0a3:2752: answers (TCP 443)
    2a02:4780:84:e624:23e1:f476:5971:3dbc: answers (TCP 443)
- www over IPv6: www.letterline.app has 2 IPv6 addresses and answers on every one we tested.
    2a02:4780:84:b6c2:a21d:5cff:ef30:6fa3: answers (TCP 443)
    2a02:4780:84:cb37:dd6f:156a:2ff4:45f6: answers (TCP 443)
- Mail servers (MX) have IPv6: No MX records, so mail goes to the domain's own address (implicit MX). It 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: HTTP 200.
    https://letterline.app/ via 2a02:4780:84:139c:3ce2:aff2:f0a3:2752 -> HTTP 200, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/euXx_Vdbqp

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

Checked 2026-11-05 14:44:01 UTC. Full DNS report: dns.pizza/domain/letterline.app · Age, certificate and blocklists: how.is/letterline.app · JSON: /api/v1/letterline.app