This is an AI-generated report. The company list, 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.