AgentMail. Cloudflare Email Service. Resend's agent SDK. Every AI SDR startup on Product Hunt this month. The pitch is always the same: "one API call and your agent has an inbox."
Cool. I went and measured the ground they're all standing on.
671,693 domains with MX records. 634,220 with SPF. 468,749 with DMARC. Daily forward-DNS scan of the Tranco top-1M, snapshot 2026-07-25.
Here's the number that should ruin your afternoon:
Last month the internet added 9,173 net new DMARC domains. DMARC enforcement went DOWN 0.42 percentage points.
Read it again. More people published DMARC. Less of the internet is protected. Three out of four of those new records were a p=none
sticker.
That is not adoption. That is dilution wearing an adoption costume.
Break the 468,749 DMARC-publishing domains down by what the record actually does:
| Category | Domains | Share |
|---|---|---|
Enforcing (p=quarantine / p=reject ) |
||
| ~231,100 | 49.31% | |
Monitoring (p=none , but reports flow) |
||
| ~120,000 | 25.61% | |
Inert (p=none , no working rua= ) |
||
| 117,384 | ||
| 25.04% | ||
| Invalid / other | ~200 | 0.04% |
That third row is my favourite thing on the internet right now.
117,384 domains publish a DMARC record with p=none
and no working aggregate report address. It blocks nothing. It reports nothing. It is a TXT record whose entire function is to make a compliance checkbox turn green.
v=DMARC1; p=none;
Twenty characters of pure theatre. Somebody billed for that. (It is, verbatim, the single most common DMARC record on the internet: 58,997 domains carry exactly that string.)
And it gets funnier when you zoom out from "inert" to "blind":
35.51% of all DMARC-publishing domains — 166,442 of them — have no workingrua=
address.
166,442 domains published an email authentication policy and then unplugged the telemetry. Some of them are on p=reject
. Think about that: they are actively bouncing mail and they cannot see whose. If a partner integration breaks tomorrow, they find out via an angry phone call in three weeks.
You would never ship a service with the metrics endpoint deleted. A third of the web ships its email policy exactly that way.
Split DMARC enforcement by Tranco rank tier:
| Tier | Enforced |
|---|---|
| top 1k | 73.05% |
| 1k–10k | 56.46% |
| 10k–100k | 43.34% |
| 100k–1M | 29.81% |
| Not in the current list | 19.10% |
The head of the internet is 3.8× more defended than the tail.
Every "email authentication is basically solved in 2026" take you have read was written by someone who checked google.com, stripe.com and their own employer, all of which live in that first row. Step outside the top 1k and most domains are wide open.
Your agent's prospects live in the tail. Your agent's customers live in the tail. Your vendors, your webhooks, your billing provider's regional subsidiary — tail, tail, tail.
The received wisdom of the last decade: nobody self-hosts email anymore, it's Google and Microsoft, give up.
Inbound mail hosting across those 671,693 domains:
| Rank | Provider | Share |
|---|---|---|
| 1 | Self-hosted | |
| 22.79% | ||
| 2 | Google Workspace | 21.83% |
| 3 | Microsoft 365 | 16.87% |
Self-hosted is the single largest category. Bigger than Google. 153,105 domains running their own MX in the year the entire industry told you it was impossible.
Google + Microsoft together are 38.70%, which is a genuinely alarming concentration number and the one everybody quotes. Nobody quotes the row above it, because it makes a decade of "just move to Workspace" content look like marketing.
Two things are true at once: the duopoly is real, and the graveyard everybody describes is full of living people.
I extracted every SPF include:
/ redirect=
target across those 634,220 SPF-publishing domains and matched them against open dictionaries of ESPs, SaaS senders and security gateways.
Classification coverage: 82.66% of include targets. That leaves 80,991 unique include targets that no public dictionary can name. And the per-domain view is worse: only 72.37% of domains that delegate through an include: come back fully classified —
This is the part that should actually scare you, and it is 100% the agent story.
Every agentic email product onboards you the same way: "add our include: to your SPF and you're done." You paste it. It stacks onto the eleven that are already there from the CRM, the ticketing tool, the marketing automation, the e-sign vendor, the abandoned 2021 webinar platform nobody has admin access to anymore.
An include:
is not a config line. It is a standing grant of permission to send mail as you. Forever. There is no expiry. There is no audit log. There is no "this include has not been used in 400 days" dashboard, anywhere, from anyone.
And SPF hard-caps at 10 DNS lookups. Blow past it and the whole record fails — not degrades, fails. Which means the way most teams discover their SPF is over budget is that legitimate mail stops arriving and nobody knows why, because — see gut punch #1 — the rua=
was never wired up.
A human SDR ramps slowly. Writes differently on Tuesday than on Thursday. Gets bored, gets sick, takes PTO. All of that accidental noise is what sender reputation is calibrated against.
An agent fleet does none of that:
Bolt that onto a domain with p=none
, no rua=
, and twelve unaudited include:
grants, and you have not built an outbound channel. You have built a very fast way to set your domain on fire, with the smoke alarm removed.
The infrastructure vendors know this — it is why the good ones now auto-configure SPF/DKIM/DMARC and warm domains for you. But their auto-config writes p=none
too, because p=none
never breaks a customer's onboarding. Everyone's incentives point at the sticker.
That's your −0.42 pp, right there.
dig +short TXT _dmarc.example.com
dig +short TXT example.com | grep spf1
dig +short TXT selector1._domainkey.example.com
Then the thirty-second triage:
rua=
first, always.p=none
p=none
without them is a lie you are telling yourself.none
→ quarantine
→ reject
. Weeks, not months. You are already late.include:
this quarter.agent.yourdomain.com
, separate DKIM key, separate reputation. When it burns — Full disclosure, because half of you are about to check my work and I would like you to succeed:
Numbers, methodology, changelog and per-domain lookup: check.live-direct-marketing.online/email-stats. CC BY 4.0, JSON API, llms.txt
, 210 archived snapshots back to 2016. Rip it apart.
We are, collectively, this week, standardising a protocol so autonomous software can act on our behalf. Tasks. Long-running jobs. Agents mailing agents.
Underneath it sits SPF: a 2003-era mechanism whose security model is a list of strings in a TXT record that nobody audits and nobody can fully identify. Sitting on DMARC, which a quarter of its adopters have configured to do literally nothing. Getting weaker, month over month, while the graph of things depending on it goes vertical.
We are not building on rock. We are building very fast, on a floor that measurably softened last month, and the smoke detector is a rua=
address that 166,442 domains never bothered to type.
Go run dig
on your own domain. Right now, before the next standup.
Bet you find something.
Data: OpenINTEL Tranco snapshot 2026-07-25, n=671,693 domains with MX. Disagree with the methodology? Good — it's published, and I'd rather be corrected than quoted.