Email Provider Market Share 2026: Who Sends the Mail | DMARCguard Skip to main content<br>14 min read Share

Who Sends the Internet’s Email? The 2026 Provider Market Share<br>Microsoft 365 sends for 19.6% of SPF-enabled domains; Google Workspace for 13.6%. That is the 2026 email provider market share on the one axis almost no chart measures — who actually sends the mail.<br>Most “email provider market share” and “email service provider market share” rankings measure something else: who people read mail in, who hosts the mailbox, or how many accounts exist. Five different datasets give five different answers about the biggest email provider because they count five different things. This post adds the missing axis, declared sending infrastructure, from our 5.5M-domain SPF supply-chain study, which parsed live SPF include: directives across the full Tranco list and ships with a downloadable CSV and JSON.<br>What you get: a ranked provider table by send-share, a methodology table that reconciles why the numbers disagree, and a transactional-ESP breakout. Every figure is dated, every figure sourced.<br>Key finding 19.6% / 13.6% of SPF-enabled domains authorize Microsoft 365 and Google Workspace to send — the two largest nodes in the global SPF supply chain<br>Source: DMARCguard SPF scan of 5,499,028 Tranco domains, 2026-03-15 Email provider market share, 2026 — the SPF-include view<br>Across 3,077,219 SPF-enabled domains in a 5,499,028-domain Tranco scan (DMARCguard, 2026-03-15), the five most-used sending providers account for 44.8% of all SPF include: directives: Microsoft 365 (19.6%), Google Workspace (13.6%), GoDaddy (6.6%), websitewelcome.com (2.5%), and Amazon SES (2.5%). Every percentage below is a share of those 3,077,219 SPF-enabled domains, mapped by their include: or redirect= directive. Each include: directive told us one thing: this domain has authorized that provider to send email on its behalf. A domain whose SPF record includes spf.protection.outlook.com is declaring Microsoft as a sender. That is the axis this post measures — “send-share” — and it is not opens, not mailbox hosting, not user accounts. SPF (RFC 7208) is, at internet scale, a delegation protocol: most domains do not send from their own infrastructure; they delegate to providers via include:.<br>Key finding 44.8% of all SPF includes belong to just five providers — Microsoft 365, Google Workspace, GoDaddy, websitewelcome.com, and Amazon SES<br>Source: DMARCguard SPF scan of 5,499,028 Tranco domains, 2026-03-15 The top-5 figure is a transparent sum of the first five provider rows (19.6 + 13.6 + 6.6 + 2.5 + 2.5 = 44.8%). Below it, the ranking spreads across hundreds of providers — from mailbox hosts to specialized transactional services.<br>#ProviderCategoryDomains% of SPF1Microsoft 365email-hosting603,85419.6%2Google Workspaceemail-hosting419,73313.6%3GoDaddyother204,6216.6%4websitewelcome.comother76,4052.5%5Amazon SEStransactional75,8172.5%6SendGridtransactional71,1692.3%7Mailguntransactional68,5622.2%8relay.mailchannels.netother67,8312.2%9Mailchimpmarketing58,7361.9%10Namecheapother51,7041.7%11Mailchimp Transactional (Mandrill)transactional49,5681.6%12Zoho Mailemail-hosting49,3611.6%13HubSpotcrm49,0151.6%

Source: DMARCguard SPF scan of 5,499,028 Tranco domains, 2026-03-15. % = share of 3,077,219 SPF-enabled domains. Microsoft 365 market share — 19.6% of SPF-enabled domains<br>Microsoft 365 is the most-used email-sending provider on the public web: 603,854 SPF-enabled domains (19.6%) authorize it via spf.protection.outlook.com, more than any other provider in a 5,499,028-domain Tranco scan (DMARCguard, 2026-03-15). The include domain spf.protection.outlook.com itself appears in 598,643 records (19.5%) — the single most-referenced SPF include on the internet.<br>The mechanics are direct: when a domain’s SPF record carries include:spf.protection.outlook.com, it authorizes Microsoft to send mail in that domain’s name and inherits every IP range Microsoft publishes. Suffix- mapping that include to a named provider is how we get from “a DNS string” to “this domain authorizes Microsoft 365 to send.”<br>How does that compare to the other ways people measure Microsoft 365? Each answers a different question, against a different denominator:<br>Installs (closest cross-check): 6sense’s email-management category puts Microsoft Office 365 at 19.97%, within 0.4 points of our 19.6% and the strongest external echo we found, but it counts company installs, not domains (2026 data). 6sense’s hosted-email cut puts Microsoft Exchange Online near 39%, roughly double, purely because the category denominator changes.<br>Revenue / seats: Gartner pegs Microsoft 365 at roughly 77% of SaaS enterprise productivity, a revenue-and-seat axis, not a domain axis.<br>Self-reported seats: Microsoft discloses over 450 million paid commercial seats (FY26 Q2, quarter ended Dec 31, 2025).<br>Four numbers (19.6%, 19.97%, ~39%, ~77%) come from four denominators answering four questions. The 19.6% is the only one that...