MX Flux: Sixteen Months of Email Records for 422 Million Domains — 71% Never Touched Their MX, Google's Lead Grows Without Switchers, and 13 Million Domains Now Refuse Mail
We followed the MX record of every apex domain across eleven full crawls, April 2025 - August 2026 (421.9 million apexes). 70.8% of mail-capable domains sit on the bit-identical MX record set sixteen months later; provider switching runs under 1% a month. Google Workspace's lead over Microsoft 365 widened at every single pass (1.28 to 1.43 by domain count) - yet direct switching between the two is a wash; the gap is made by new domains, which arrive 2.3-to-1 for Google, while Microsoft wins the migrations out of self-hosting. Null MX quadrupled from 3.4M to 13.4M domains, and 77% of it is one aftermarket platform's zone template. For email and security teams, hosting providers, and Internet measurement researchers.