By the team at MailTester Ninja — a real-time email verification API that stores nothing.
Everyone says "IPv6 is here." For the web, mostly true. For email, it is a mirage.
We resolved the MX records of 50,000 of the most-linked domains and checked whether any of their mail servers publish an AAAA record, meaning they can actually receive over IPv6. No sending, no personal data, just DNS.
55.2% of mail-enabled domains have at least one IPv6-capable MX. That sounds healthy. It is not, because two companies carry almost the whole number:
| Email provider | IPv6 MX |
|---|---|
| Other / self-hosted | ██░░░░░░░░ 18.4% |
| Google Workspace / Gmail | ██████████ 100% |
| Microsoft 365 / Outlook | █████████░ 91.3% |
| Proofpoint | ░░░░░░░░░░ 0.6% |
| Mimecast | ░░░░░░░░░░ 0% |
| Tencent QQ | ░░░░░░░░░░ 4.2% |
| Namecheap | ░░░░░░░░░░ 0.2% |
| Cisco IronPort | ░░░░░░░░░░ 4.5% |
| Zoho | ░░░░░░░░░░ 0% |
| Barracuda | ░░░░░░░░░░ 0% |
Google (100%) and Microsoft (91.3%) run IPv6 on nearly every inbox. Remove those two, the providers that already anchor most of the world's mail, and IPv6 email adoption falls from 55.2% to 12.9%. The enterprise security gateways that gate corporate mail, such as Proofpoint, Mimecast and Barracuda, are effectively not on IPv6 at all.
Why it matters for deliverability. IPv6-only sending is a dead end. It reaches Gmail and Outlook and little else. Dual-stack is not optional. IPv4 is still the backbone of email, and that is where blocklists, FCrDNS and IP reputation are mature. The takeaway: IPv6 email is not adopted. Google and Microsoft adopted it for you. Plan your sending for an IPv4 world with two big IPv6 exceptions.
Check any domain yourself — our free deliverability analyzer shows a domain's MX / SPF / DMARC in one click (no signup, nothing stored). Need to confirm whether a specific mailbox actually exists and is deliverable? That is exactly what MailTester Ninja's email verifier does in real time — and we store no data.
Source: MailTester Ninja's open Email Infrastructure Index — a live DNS scan of 50,000 of the world's most-linked domains, updated daily, aggregate only. Free to cite under CC BY 4.0. Snapshot: Sat, 11 Jul 2026 12:39:35 GMT.
Top comments (0)