Self-hosted email use has halved since 2016, data shows

The share of top-million domains running their own email server has dropped from 44.6% in 2016 to 22.4% today, according to researcher Artem Berezin, who works at business email company Live Direct Marketing. Writing on the Internet Society's blog, Berezin says the decline is still moving, down roughly half a percent in the last 30 days alone.

Google Workspace now handles 21.8% of detectable MX records and Microsoft 365 another 16.8%, meaning the two companies together receive mail for 38.6% of the domains studied. Berezin built the analysis from daily DNS snapshots captured by the University of Twente, SURFnet, and SIDN Labs' OpenINTEL project, matched against the Tranco project's list of the most popular domains.

Self-hosting still edges out either single provider, but Berezin frames the concentration as a real risk for anyone who depends on mail actually arriving. Unlike a CDN outage, a rejected message has no fallback, it's simply gone. He also found that more than half of DMARC records currently published have no enforced policy, meaning many domains still can't fully verify that a message claiming to be from them is authentic, despite Google and Yahoo's 2024 bulk-sender rules requiring DMARC.

For anyone running their own mail server or self-hosted stack (Postfix is the example Berezin names directly), the practical takeaway is deliverability risk: as Google and Microsoft's filters increasingly define what counts as trustworthy mail, a fresh self-hosted server has a harder time getting accepted at scale than it did a decade ago, independent of whether it's actually sending legitimate mail.