Two Providers, a Stubborn Plateau and a Very Long Tail: Email in the Tranco Top-1M
• 7 min read
Ten years of DNS measurements reveal three trends across the Internet's most popular domains: email continues to consolidate around two providers, DMARC enforcement has hit a plateau, and a surprisingly large long tail of infrastructure defies easy classification.
“I'm one of those nutjobs running my own mail servers (on OpenBSD, no less). It's a small pair of servers, with < 10 domains attached, all used by my family. Regarding dmarc: I already have enough problems getting mail into google (usually marked as spam) or hotmail (which for some reason claims I'm on a block list -- this is not unusually, I understand, judging by the somewhat constant comments in the mailop mailing list). I have considered moving to p=quarantine, but I don't yet have rua set up for auto-processing. Frankly, it's kinda annoying, since everyone seems to send different formats. I would GREATLY prefer that there be an API so I could set up an endpoint to process these. Anyway, there you have it: I fear adding p=quarantine would make things worse (though, it might actually make it better), and I don't have time in my life (since it's clearly a hobby) to process the reports.”
Fair points. On the reports: the aggregate rua XML is one schema (RFC 7489), it's the forensic ruf ones that vary, and parsedmarc eats all of them and outputs JSON. That's about as close to your API as it gets today, one evening of setup. On Hotmail: that block list message is almost always Microsoft's internal list, not a public RBL. The delist form is at https://olcsupport.office.com/ (Sender Information for Outlook.com Delivery). The process is its own kind of pain, the form keeps moving and sometimes you get silence or a canned reply, but when it works they do delist small senders, so worth a shot before anything else. And on quarantine: for aligned mail it's safer than it feels. Start with pct=25, the only thing that really suffers is mailing list traffic like mailop, and that breaks regardless of your policy.
“While not trying to hide methodological problems and validity issues, which are always an issue with these active scanning probes, the decline of self-hosting is also what I observed about six years ago. While that is hardly surprising as such, what I also observed was that about 1/4 of "popular domains" (scare quotes intended) had their MX records pointing to two vendors, Microsoft and Google. That is a little more interesting, I reckon. https://arxiv.org/pdf/2002.10731”
Thanks, I hadn't seen that paper. Your 24% for Google plus Microsoft in the November 2019 data is 38.6% in my July 2026 snapshot, so the trend held at roughly two points a year. Metrics aren't identical though: you counted domains with at least one MX at either provider, I take only the primary MX, so mine is the stricter number.
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