In 2016, 44.6% of MX-publishing domains in the top million ran their own mail server. In the 18 July 2026 snapshot that figure is 22.4% - and it is still falling, down another half a percentage point in the last thirty days alone.
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The domains didn't disappear; they moved. Google Workspace now receives mail for 21.8% of MX-publishing domains and Microsoft 365 for 16.8%. Together that is 38.6% of the measured Internet's inbound mail behind two companies. Nobody else comes close: the next named provider, Proofpoint, sits at 1.9%.
It is easy to read this as a market-share story, but for this community it is really a resilience story. The RIPE community has spent years discussing DNS and CDN centralisation; email is following the same path, just more quietly. When more than a third of popular domains depend on two providers to receive mail, an outage, a filtering change or a policy decision at either one propagates through the whole ecosystem at once. And unlike a CDN, email has no graceful fallback - a rejected message is simply gone.
There is a second-order effect too. The fewer independent operators there are, the more the remaining ones inherit the deliverability problems of a world tuned for the big two. Anyone who has tried to stand up a fresh Postfix box in 2026 and get its mail accepted at scale knows exactly what I mean.