Self-hosted email is in steep decline, Microsoft and Google are taking over

The number of large users hosting their own email servers has halved in the last decade, according to Artem Berezin, a researcher who works at business e-mail company Live Direct Marketing. On the Internet Society blog, Berezin explained that DNS records reveal a lot about email. The MX record says where the mailbox lives. The SPF record says who may send on the domain's behalf. The DMARC record says what should happen when a message fails authentication," he wrote. Berezin says he analyzes those records using daily forward-DNS snapshots captured by the OpenINTEL project run by the University of Twente, SURFnet and SIDN Labs. He also consults the Tranco project's assessment of the most popular domains to determine the million most popular domains, then classifies each domain's MX hostname and SPF includes against open dictionaries of mailbox providers, sending platforms and SaaS applications." The data he uses goes back to 2016, but he admits the dictionaries he accesses don't offer a complete view of the world's email servers. His lead finding is that in 2016, 44.6 percent of the top million domains ran their own mail server. In 2026, that's down to 22.4 percent. The number of self-hosted mail servers is falling fast - down by half a percent in 30 days. Self-hosting an email server remains the most common way to process mail, however Google Workspace is hot on its heels with 21.8 percent of detectable MX records, ahead of Microsoft 365's 16.8 percent. Berezin thinks the fact that two tech giants handle 38.6 percent of email is concerning. The RIPE [NCC] community has spent years discussing DNS and CDN centralization; email is following the same path, just more quietly," he wrote. 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." Postfix is a FOSS mail server. Berezin's reference to the struggle to get mail accepted at scale reflects the fact that Google and Microsoft operate filters to detect messages they believe come from untrustworthy sources. If those two tech giants don't accept messages from Postfix or other sources, they make their own services more attractive - marketers who want their email blasts to land will move to the service providers most likely to let their messages through. Another thing that worries Berezin is the use of DMARC (Domain-based Message Authentication, Reporting, and Conformance) records - the instruction in DNS settings that tells email servers how to handle emails that fail an authenticity check. His research found that over half of DMARC records have no valid policy or monitor email without enforcing policies. That low rate is happening despite Google and Yahoo changing their bulk sender requirements in 2024 to require use of DMARC. At what concentration does inbound mail become a systemic dependency worth the community's explicit attention?" Berezin asks. What would actually move DMARC from published to enforced, given that the 2024 mandates demonstrably did not do so? And how much of the Internet's mail infrastructure are we all failing to see because our dictionaries don't know its name?" Berezin wrote that he can't answer those questions but hopes his daily download of email server data and ongoing analysis means he can one day. (R)