This is an AI-generated report. The lists, domain matching, DNS lookups and analysis were produced by an AI agent (Claude). Findings are drawn from live DNS records and are believed accurate as of 3 August 2026, but domain matching is imperfect and the numbers have not been independently reviewed — verify anything you intend to rely on.

MX record survey · August 2026

Who really runs the world's biggest mailboxes

Live MX and SPF lookups against the primary domain of 1,150 companies — the top 1,000 of the Forbes Global 2000 plus 150 AI-native and private cloud firms — broken down by sector.

The overall split

Microsoft 365 serves nearly half of these companies outright. Self-hosted mail is far from dead: roughly one in five still runs its own inbound infrastructure, concentrated in Chinese state-owned groups, Japanese conglomerates and the largest US banks.

    The AI-native split is the story

    Split the same population by vintage and the pattern inverts. Established global corporates run on Microsoft; the AI and private-cloud generation runs on Google Workspace by a factor of roughly nineteen to one.

      By sector

      Sorted by number of companies. Hover any segment for exact counts. Oil & gas, healthcare and hospitality are the most heavily Microsoft-weighted; banking carries the most self-hosted mail; the two technology tiers built since 2015 are the only ones where Google leads.

        Security gateways hide the backend

        A gateway in front of the mailbox rewrites MX, so the platform behind it is invisible to a plain MX lookup. Recursively expanding each domain's SPF chain and checking its autodiscover record unmasked most of them; the rest are counted separately rather than guessed at.

        Gateway vendors in front of these domains

        Counted wherever a gateway fronts the MX, whether or not the backend was identified.

        What sits behind them

        By headquarters country

        Countries with at least 12 companies in the sample. The self-hosted share tracks state ownership and data-residency rules more than company size.

          Every company

          All 1,150 rows, with the domain checked and the first MX host returned. Click a column heading to sort.

          RankCompanySector CountryDomainMail platform First MX host

          How this was measured

          Building the list

          • Ranks 1–1,000 of the Forbes Global 2000 (2026), which carries an industry label and headquarters country per company.
          • Plus the Forbes AI 50 (2026 and 2025) and Cloud 100 (2025) — 150 firms after de-duplication, including OpenAI, Anthropic and Cursor, which no revenue-ranked list would reach.

          Finding the right domain

          • Candidates from Wikidata (official website) and Clearbit, scored on source agreement, name similarity, TLD shape and live DNS.
          • The website domain is often not the mail domain — jpmorganchase.com publishes no MX; mail runs on jpmorgan.com. Where the site domain had no MX, sibling domains were probed and confirmed.
          • 114 domains were corrected by hand where automated matching picked a same-name but unrelated entity — Alphabet resolving to BMW's fleet-leasing arm, Williams to Williams College, Taiwan Semiconductor to the industry association.

          Reading the records

          • MX and TXT resolved over DNS-over-HTTPS against Cloudflare and Google. An earlier UDP scan produced rate-limit false negatives — every no-MX result was re-checked, and 34 domains that genuinely do publish MX were recovered.
          • MX hostnames matched against ~110 provider signatures, including newer forms such as <tenant>.mx.microsoft.
          • Behind a gateway, each domain's SPF include: chain was expanded recursively and its autodiscover CNAME checked.

          Where to be careful

          • domains still sit behind a gateway with no backend disclosed. of those publish a Microsoft tenant-verification record — suggestive, but large organisations often hold a tenant for Entra or Teams while mail stays elsewhere, so it is reported separately and not counted as Microsoft 365.
          • A domain-level check reads the primary domain only. Groups running several mail platforms across subsidiaries appear once, under whichever platform serves the flagship domain.
          • 7 domains publish no MX at all — usually a holding-company domain that never carries mail.
          Sources: Forbes Global 2000 / AI 50 / Cloud 100 list data; Wikidata; Clearbit Autocomplete; live DNS via Cloudflare and Google DNS-over-HTTPS. Records resolved 3 August 2026 — DNS changes, so treat this as a snapshot.