AAAA Record Lookup: IPv6 Address Resolution
Look up AAAA records to find IPv6 addresses for a domain. Understand dual-stack DNS, when AAAA records matter, and how to verify IPv6 connectivity.
What AAAA Records Are
A AAAA record (pronounced "quad-A") maps a domain name to an IPv6 address, as defined in RFC 3596. Where an A record returns a 32-bit IPv4 address like 93.184.216.34, a AAAA record returns a 128-bit IPv6 address like 2606:2800:220:1:248:1893:25c8:1946. The name "AAAA" reflects the fact that IPv6 addresses are four times the length of IPv4 addresses.
Why IPv6 Matters
IPv4 address space is exhausted. The last blocks were allocated years ago, and new allocations come through transfers and reclamation. IPv6 was designed to solve this — its 128-bit address space is effectively unlimited. Adoption has been steadily climbing: major networks, cloud providers, and mobile carriers now route IPv6 natively.
For email, IPv6 adoption has specific implications. Large receivers like Google and Microsoft accept mail over IPv6, but they apply stricter reputation checks on IPv6 senders because the address space is newer and has less established reputation data. If your mail server publishes a AAAA record, make sure the IPv6 address has a valid PTR record and is not on any blacklists.
Dual-Stack Configuration
Most domains that publish AAAA records also keep their A records in place. This dual-stack approach lets IPv6-capable clients use the faster path while IPv4-only clients still connect. DNS resolvers with IPv6 connectivity will prefer AAAA records when available, but fall back to A records transparently.
To verify dual-stack is configured correctly, run both the A Lookup and AAAA Lookup for your domain. Both should return valid, reachable addresses.
Common AAAA Record Issues
Missing AAAA record. Not necessarily a problem — many domains operate on IPv4 only. But if your hosting provider assigned you an IPv6 address, publishing the AAAA record ensures clients that prefer IPv6 can reach you directly instead of falling back through NAT64 or other translation mechanisms.
AAAA record with no working IPv6. Publishing a AAAA record for an address your server does not actually listen on causes connection timeouts for IPv6 clients before they fall back to IPv4. This is worse than having no AAAA record at all — it adds latency to every connection.
IPv6-only mail server without PTR. Sending mail from an IPv6 address that lacks a reverse DNS (PTR) record will trigger rejection at most major receivers. Always configure forward and reverse DNS together.
Checking AAAA Records
Use the mxio AAAA Lookup to query IPv6 addresses for any domain. If you need to check both IPv4 and IPv6 records together, the DNS Lookup tool lets you query any record type in a single interface.
Related Articles
Look up A records to find the IPv4 addresses a domain resolves to. Understand what A records do, how DNS resolution works, and how to diagnose common issues.
Use the DNS Lookup tool to query any DNS record type — A, AAAA, MX, TXT, CNAME, NS, PTR, SOA — and understand what each record type does.