Microsoft 365 Market Share 2026: It Runs Email at 71% of US Public Companies, Google at 12%

Microsoft 365 market share depends on who you count. We looked up the mail records of 123,995 domains on October 29, 2026: Microsoft 365 handles email for 71.3% of US public companies, 76.8% of FDIC-insured banks and 70.5% of .gov domains, against 12.0%, 1.5% and 10.5% for Google Workspace. Among the top 100,000 websites it is close: 31.5% to 27.4%.

Every Microsoft 365 market share figure on the first page of Google comes from a vendor that sells company technology lists, and none of them publishes its method. This one is measured. A company’s MX record is public, and it names the server that receives the company’s email. Microsoft 365 mail goes to a host ending in mail.protection.outlook.com; Google Workspace mail goes to smtp.google.com or aspmx.l.google.com. We looked up those records for four lists of real organizations and counted.

The answer to “Microsoft or Google?” turns out to be a question about who you are counting. US public companies pick Microsoft over Google by about 6 to 1, and banks by about 51 to 1. The global web is close to an even split, and at the very top Google is ahead.

The test: large US companies vs the long tail

The chart splits each list into tiers. Among US public companies, Microsoft 365’s share is high at every size, from 65.2% of companies with a $10 billion-plus public float to 68.7% of those under $250 million. Google’s best showing is among the smallest public companies (15.7%). Banks are the most Microsoft-heavy group we measured: Google Workspace handles 1.5% of bank domains. In the .gov registry, counties (74.7%) and cities (72.3%) lean further toward Microsoft than federal domains (49.2%), where 27% of mail domains route to their own or another agency’s servers.

Share of domains with a working MX record. “Inferred” means the MX points to a filtering gateway and the domain’s SPF record authorizes only that platform, or the autodiscover record points to Microsoft. Hover for counts.

The long tail looks different. Of the top 100,000 websites in the Majestic Million, 76,178 accept email. Microsoft 365 receives mail directly for 23.6% and Google Workspace for 26.7%; counting gateway customers whose backend we can infer, Microsoft reaches 31.5% and Google 27.4%. Among the 1,000 most-linked sites, Google leads, 35.5% to 28.0%. The rest of the long tail is spread across Chinese and Russian mail platforms, web hosts, forwarding services and self-run servers.

Behind the gateways: what Proofpoint and Mimecast customers run

Big companies make direct measurement harder. 57.8% of US companies with a $10 billion-plus float point their MX at a filtering gateway rather than at their mailbox platform, and 249 of those 564 large-cap mail domains use Proofpoint. The mailbox behind the gateway is not in the MX record, so we used two other public records. The SPF record lists the servers allowed to send a domain’s mail; if it includes spf.protection.outlook.com and not Google’s, the domain almost certainly sends from Microsoft 365. The autodiscover record tells Outlook where a mailbox lives; a CNAME to autodiscover.outlook.com points to Exchange Online.

All 15,126 gateway domains across the four lists. Share at the right is Microsoft 365 by either signal.

The two signals agree. Of the 7,883 gateway domains whose SPF pointed only to Microsoft, 77.9% also had a Microsoft autodiscover record and 93.0% had either that or a Microsoft 365 domain verification token (MS=ms...) in DNS. We then used autodiscover to classify 2,781 gateway domains whose SPF was silent or listed both platforms. That leaves 3,794 gateway domains (25.1%) we cannot assign. For Proofpoint, 68% of its 1,658 unassigned customers list only Proofpoint’s own servers in SPF, which is what DNS shows when outbound mail also leaves through the gateway. Because of that residue, the Microsoft share for large companies is a floor: between 65.2% and 84.4% of $10 billion-plus companies, depending on where the unassigned gateway customers sit.

Microsoft 365 vs Google Workspace by country

Country-code domains among the top 100,000 show where each platform is strong. Microsoft 365 leads in the United Kingdom (60.1% vs 13.9%), the Netherlands (61.3%) and Germany (31.2% vs 7.3%). Google leads on .io (68.9%) and .ai, startup favorites. In Russia and China Microsoft barely registers (0.2% and 1.5% of mail domains): self-run servers, Yandex and VK lead in Russia, and Tencent, NetEase and Alibaba in China.

Top-level domain from the Majestic Million record. A country-code domain is a proxy for the site’s market, not proof of where the company is based.

Every provider we found

Microsoft and Google are not the whole market. The table counts every provider with a meaningful presence in at least one list, with each provider’s share of that list’s mail domains. Gateways appear here by their own name; the census chart above reassigns their customers where the backend can be inferred.

Security panel: DMARC policies

We also read each mail domain’s DMARC record, the policy that tells receiving servers what to do with mail that fails authentication. Banks and public companies are the strictest: 43.7% of bank domains and 37.2% of public company domains publish p=reject. The .gov registry is the weakest of the US lists, with 33.2% of mail-enabled .gov domains publishing no DMARC record at all. Among the top 100,000 websites, 60.2% of domains on Microsoft 365 publish quarantine or reject, against 49.5% on Google Workspace, 65.0% behind gateways and 35.4% on self-run servers.

Policy from the p= tag of the _dmarc TXT record. Domains with more than one DMARC record or no p= tag are counted as invalid and left out of the bars (310 across the four lists).

A DMARC policy of p=none only monitors; it does not stop spoofed mail. Google’s sender guidelines have required bulk senders to Gmail to publish DMARC since February 1, 2024, but accept p=none. For the phishing side of this, see our phishing statistics from four primary sources.

Why the published market share numbers disagree

The pages that rank for this query report Microsoft anywhere from 11% to about 45%, and Google from about 50% to 73%. They are counting different things. We read each one:

Microsoft’s own annual report gives no share figure or seat count for fiscal 2026, only growth: “Microsoft 365 Commercial seats grew 6% driven by small and medium businesses and frontline worker offerings.” Our census measures something narrower and checkable: for a named list of domains, which platform receives the mail today. It does not count users, seats or revenue, and one large company and one small blog each count once.

What this means for MSPs

1. In US business, Microsoft is the default you will inherit. 71% of public companies, 77% of banks and 70% of .gov domains run on Microsoft 365. A practice built for regulated US clients needs deep Microsoft 365 skills first; Google Workspace is the exception, most common among smaller and tech-led firms.
2. Check a prospect’s MX before the first call. The method on this page works on any domain in seconds: MX, SPF include, autodiscover CNAME. It tells you the platform, whether there is a gateway in front of it, and which gateway.
3. Gateways are a large-account pattern. 58% of $10B-plus companies and 46% of banks put a filtering gateway in front of their mailboxes, against 12% of the top 100,000 websites. If you sell email security, the bank and enterprise segments already buy it; the long tail mostly relies on the platform’s built-in filtering.
4. DMARC is the fastest visible fix. 33% of .gov mail domains and 22% of the top 100,000 have no DMARC record, and many more sit at p=none. Moving a client from none to quarantine to reject is cheap, measurable work. Pair it with phishing-resistant sign-in; our MFA statistics show how few services support it.
5. Price changes will hit most of your clients. Given these shares, the July 2026 Microsoft 365 price increase reaches the large majority of US business clients at their next renewal.

Frequently asked questions

What is Microsoft 365’s market share?

It depends on the population. In our October 2026 DNS census, Microsoft 365 receives the email of 71.3% of US public companies, 76.8% of US banks and 70.5% of US government .gov domains that accept mail, but 31.5% of the top 100,000 websites worldwide. Shares count domains, not users or revenue.

Is Google Workspace bigger than Microsoft 365?

Not among US organizations: Google Workspace handles 12.0% of US public company domains and 1.5% of banks. It does lead among the most-linked websites, with 35.5% of the top 1,000 versus 28.0% for Microsoft 365, and among .io and .ai domains, where it handles 69% and 78%.

Do large companies use Microsoft 365 or Google Workspace?

Mostly Microsoft. Among US public companies with a public float of $10 billion or more, at least 65.2% route mail to Microsoft 365 and 8.9% to Google. Another 19.1% sit behind a filtering gateway (usually Proofpoint) whose backend DNS does not reveal, so the Microsoft figure is a floor.

How can you tell if a company uses Microsoft 365?

Look up its MX record. Microsoft 365 mail goes to a host ending in mail.protection.outlook.com (or mx.microsoft for DNSSEC-enabled domains). If the MX points to a gateway such as Proofpoint or Mimecast, check the SPF record for include:spf.protection.outlook.com and whether autodiscover. points to autodiscover.outlook.com.

How many companies enforce DMARC?

37.2% of US public company domains publish p=reject and 28.3% p=quarantine; 13.3% have no DMARC record. Banks are stricter (43.7% reject). Among the top 100,000 websites, 22.3% have no record and 31.0% only monitor with p=none.

Methodology

References

1. Majestic, The Majestic Million (CC BY 3.0). Accessed October 2026.
2. U.S. Securities and Exchange Commission, EDGAR APIs: XBRL frames (dei:EntityPublicFloat) and filing archives. Accessed October 2026.
3. FDIC BankFind Suite API, institutions endpoint. Accessed October 2026.
4. CISA, dotgov-data: current-full.csv (CC0 1.0). Accessed October 2026.
5. Google Public DNS, JSON API for DNS over HTTPS and Quad9. Accessed October 2026.
6. Microsoft Learn, Add DNS records to connect your domain (MX mail.protection.outlook.com, SPF include:spf.protection.outlook.com). Accessed October 2026.
7. Microsoft Learn, How SMTP DNS-based Authentication of Named Entities (DANE) works (mx.microsoft MX values). Accessed October 2026.
8. Google Workspace Admin Help, Google Workspace MX record values and Define your SPF record. Accessed October 2026.
9. Google, Email sender guidelines. Accessed October 2026.
10. RFC 7208, Sender Policy Framework; RFC 7489, DMARC; RFC 7505, Null MX. Accessed October 2026.
11. Microsoft Corporation, Form 10-K for the fiscal year ended June 30, 2026. Accessed October 2026.
12. Pages ranking for “Microsoft 365 market share”, as cited in the comparison table: 6sense (two pages), Enlyft and Onix. Accessed October 2026.