Email deliverability in the age of AI inboxes

A few weeks ago I wrote about how the emails from a certain brand sitting in someone's inbox showed up in over half of the AI answers AI overivew gave to that person. Some of you replied, and the same question kept coming back in different words: fine, but how do I make sure my email actually arrives and it doesn’t land in spam?

So I pulled my own numbers. Across my last five issues, 98 to 100 % of my emails were delivered, my bounce rate sat around half a percent with zero hard bounces, and I have not had a single spam complaint.

Here is what I do. Most of it is not technical at all, and the part that is takes one afternoon.

The inbox changed this year

In early 2026 Gmail moved into what Google calls its Gemini era. AI summaries now condense your email into a few lines. Prioritisation decides what surfaces first. And a new AI inbox filters out whatever it judges unimportant.

Gmail has around three billion users and accounts for a quarter to a third of all email opens worldwide. So for a large slice of your list, an AI reads your email before the human does, and forms an opinion about whether the human should even bother having and receiving that email. Here of course I largely talk about promotional, business and newsletter like emails. Personal emails are another story.

Folderly tracked what happened next. Open rates rose to around 45 percent after AI summaries launched, while click-through rates fell from 4.35 to 3.93 percent. That’s a clear correlation that people are reading only the AI summary instead of manually reading the email.

That is the new way the inbox works, an agent deciding if that email is even worth you reading it or it better lands in your spam folder.

Why this is a distribution problem

I keep coming back to the same idea that your email list is the one distribution channel you own the most.

That is still true, with one condition attached. You own the list. You do not own the delivery. Every message passes through infrastructure you have little control over, and that infrastructure got a lot stricter. Since November 2025, Gmail rejects non-compliant mail from large senders outright, so it never reaches spam. Microsoft did the same for Outlook and Hotmail. Those providers plus Yahoo cover roughly 90 percent of email users.

So deliverability is acting like a gate on the only channel you own the most of. If your email lands in spam, that recipient is a lost opportunity in the same way as if that email wouldn’t have even landed.

Part one: the things anyone can do

None of this needs a technical background to achieve. It is mostly about how you treat your list and how you write.

Only email people who asked (opted in). Every bought list and every address you added without permission is a complaint waiting to happen so I would avoid that as much as possible. If you decide on doing cold outreach better use a burner email address that you would warm up first.

Keep complaints near zero. The hard limit is 0.3 percent, and stable senders work to a tighter ceiling around 0.1 percent. On a list of 200 people, that is less than one complaint. And as the scale increases, that matters even more.

Make leaving easy. It sounds like inviting people out but in practice it is your best protection against reaching the spam inbox. Somebody who cannot find the unsubscribe button will hit the spam button instead.

Clean the list. People who never open drag your engagement signals down, and old addresses turn into spam traps. Cutting long term non-openers feels like going backwards but your delivery gets better.

Be predictable. I send once a week, same morning. Steady volume and timing build a stable reputation. Sudden bursts after months of silence look exactly like spam to the systems.

Put your point at the top. This is the one that is new. If an AI summarises your email before your reader sees it, anything that does not make the summary effectively does not exist. Your main idea belongs in the first line or two, in plain language.

One email, one purpose. Messages that try to do three things get summarised into a vague blur. Have a clear purpose for each email that you send.

Match your subject line to the body. A clever subject that does not reflect the content reads as bait to a person and as low quality to a machine.

There is a nice consequence buried in those last three. Content quality has quietly become a deliverability signal. Gmail's AI is judging clarity and structure. Writing well is now technically useful.

Part two: the technical side

This next part is genuinely technical, so I want to flag it clearly. If you have someone technical on your team, hand this section to them and they will know exactly what to do with it. If you are on your own, it is very googleable/claudable, and your email platform almost certainly has a step by step guide for your specific domain provider. It takes an afternoon once, and it makes a big difference.

What you need in place is SPF, DKIM and DMARC. These are authentication records you add to your domain, and they prove your email is really coming from you. Without them, providers reject your messages before any human judgement happens.

Two details that are worth passing on to whoever does the work:

Alignment matters, not just presence. The domain in your From address has to align with the domain validated by SPF or DKIM. Records that exist but do not align get flagged faster than they used to.

Start DMARC at p=none, then tighten it. Monitoring mode is an accepted starting point. The expectation now is that you progress toward quarantine and then reject over time.

While someone is in there, two more small jobs. Turn on one click unsubscribe, which puts the unsubscribe option directly in the email header(according to RFC 8058). Most platforms have it as a setting and plenty of people never switched it on. And sign up for Google Postmaster Tools, which is free and shows your reputation and complaint rate the way Google sees it. Almost nobody does this.

The gap it closes is large. Senders with this set up correctly average around 89 percent inbox placement. Senders missing pieces see 22 to 34 percent of their mail routed to spam. Roughly 30 percent of senders are failing at least one requirement right now, usually without knowing.

Your thirty minute check

Anyone can do these today:

1. Open your last three sends and check your bounce and complaint rates. If complaints are above 0.1 percent, fix that before anything else.

2. Confirm one click unsubscribe is switched on in your email platform.

3. Pull everyone who has not opened anything in six months. Send one reactivation email, then remove the rest.

4. Read your last issue and ask whether the main point is in the first two lines. If it is not, move it.

You or someone technical:

5. Send yourself a test email at a Gmail address. Open it, choose Show original, and confirm SPF, DKIM and DMARC all say PASS.

6. Run your domain through a free DMARC checker and confirm the record exists and matches your sending domain.

7. Sign up for Google Postmaster Tools and add your domain. Check back in a week.

What I'm Thinking About This Week

How strange it is that writing clearly became a technical requirement. For years clarity was a nice quality that good writers had. Now an AI reads your email first, decides what it is about, and decides whether it is worth surfacing. Writing plainly and putting your point up front has quietly turned into infrastructure.

Reply to this email with one of:

• Run the Gmail test above and tell me whether you passed all three checks. I am curious how many people are quietly failing one.

• Have you ever opened Google Postmaster Tools? Most people never have.

• What is your complaint rate right now, and did you know it before today?

P.S. The toolkit, in the order I would use it: Visibility Audit → GEO/AEO Audit Checklist → How to Get Cited by AI → SEO Strategy Playbook → Title & Meta Audit → Sovereign Idea Workflow. All free.

P.P.S. Know someone who has built a list and never checked whether it actually arrives? Forward this. The check takes thirty minutes and it protects the only channel they own. They can subscribe at thesovereigntechnologist.com.

That’s all for this week.

See you next Thursday.