For years, the inbox gave you three chances to earn an open: the sender name, the subject line, and the preview text. You wrote all three. Most marketers spent real time on each one.
That's changing. On a growing number of devices, the line under your subject is now a sentence written by an AI model that read your email and decided what it was about. Subscribers often decide what to do based on that sentence, and some never open the email at all.
What effective looks like is shifting. The emails that do well in an inbox with summaries are the ones whose main point is easy to find, and whose senders have built a history of engagement that inbox providers recognize.
Where AI Summaries Show Up Today
Summaries work differently depending on the email app, and the details matter. Some appear automatically in the inbox list. Others appear only when someone opens a long thread or asks for one.
| Email app | What subscribers see | Automatic? | Who gets it |
|---|---|---|---|
| Apple Mail | A one- or two-line summary replaces your preview text in the inbox list | Yes, for unread email | iPhone, iPad, and Mac users with Apple Intelligence, on by default |
| Gmail (Gemini summary cards) | A summary card at the top of longer emails and threads | Yes, on long messages | Paid Google Workspace and Google AI plans, in the mobile app |
| Gmail (AI Overviews) | A summary when opening a thread with many replies | Yes, on long threads | All users, starting in the U.S. in English |
| Outlook | A summary after clicking "Summarize" | No, on request | Windows Outlook users, including many without a Copilot license |
Apple Mail is where marketing emails are most likely to be summarized today. Apple's own Mail user guide states that a short summary automatically appears under each unread email, in place of the first lines of the message. Apple Intelligence has been on by default on supported devices since early 2025, so many of your subscribers see summaries without ever choosing them.
Apple Mail also sorts incoming email into Primary, Transactions, Updates, and Promotions, and on devices with Apple Intelligence it moves messages it considers urgent to the top of Primary. Gmail has made a similar shift in its Promotions tab, where a "most relevant" view favors brands each person engages with.
Gmail's automatic summaries are aimed mostly at long threads and paid accounts, so a single promotional email to a consumer Gmail address usually still shows your own preview text. That's likely to change as these features expand.
How Subscribers Act on What the Summary Says
The more important question is what people do after reading a summary. In June 2026, Validity published a survey of 1,000 U.S. consumers on exactly this. It found that 55% make decisions based on AI summaries without reading the full email. That 55% breaks down into 35% who skip the full message, 15% who don't open it at all, and 5% who delete it.
The same survey found that only 10% of consumers fully trust summaries to be accurate, and 15% have turned AI email features off. That combination is worth sitting with. Many subscribers act on summaries they don't completely trust, which means a vague or misleading summary of your email can cost you a click even when the email itself was strong.
For marketers, the summary has become part of the message. Your subject line still matters, but for a growing segment of readers, the AI's description of your email does a lot of the work the preview text used to do.
Write the Opening So the Summary Gets It Right
Neither Apple nor Google documents exactly how their summaries are generated, or which parts of an email they weigh most. What's reasonable to assume is that a model summarizing an email will describe what the email most clearly says. An email whose main point appears early, in plain words, is easier to summarize accurately.
That leads to a few concrete habits. State the purpose of the email in the first two or three sentences. If there's an offer, name it with its specifics: the discount, the product, the deadline. If there's a date, write the date. A summary that reads "30% off winter coats through Sunday" gives a subscriber a reason to open. A summary that reads "The brand shares seasonal updates" gives them a reason to move on.
Clever openings that build suspense before revealing the point tend to work against you here. The model has to summarize something, and if the first lines are a setup, the summary may describe the setup.
Clear structure helps the reader too. Short paragraphs, descriptive headings, and a call to action that says exactly what happens next make an email easier to understand for a person scanning it and for a model summarizing it. Writing for one tends to serve the other.
Test What the Summary Says Before You Send
Most marketers preview a campaign on desktop and mobile before it goes out. Summaries add one more check, and it takes only a few minutes.
Send a test of your campaign to an iPhone or Mac with Apple Intelligence turned on and leave it unread. Look at the inbox list and read the summary under your subject line. Then ask a simple question: if this sentence were the only thing a subscriber read, would they know what the email offers and why it matters to them?
If the summary describes your greeting, your brand story, or a general "update," the main point of the email is probably buried. Move it higher and test again.
It also helps to compare the summary against your subject line. When the two describe the same thing, the subscriber gets a consistent message twice. When they describe different things, the email can seem unfocused before anyone opens it.
Over time, these checks show patterns. Some formats, like a single featured product or a clear deadline, tend to produce accurate summaries. Others, like long newsletters covering five unrelated topics, tend to produce generic ones. That's useful information for planning which content goes in which email.
Preview Text Still Matters for Part of Your List
Preview text still reaches a large share of your subscribers. Many people read email in apps that don't summarize marketing messages automatically, including most consumer Gmail accounts and Outlook. Apple Mail users can turn summaries off with a single setting, which restores the first lines of each message. And some subscribers will be on older devices that don't support Apple Intelligence at all.
The practical answer is to treat preview text and the email's opening as one unit. Write preview text that states the main point, and make sure the first lines of the email say the same thing. Whichever version a subscriber sees, the AI's or yours, the message comes through.
Why Open Rates Got Less Reliable
Summaries add to a measurement problem that was already building. Since 2021, Apple Mail Privacy Protection has preloaded images in email, including the tracking pixels used to record opens. That registers many emails as opened whether or not anyone read them.
Gmail made a change in late 2025 that moved in the other direction. According to Validity's analysis of the Gmail open-rate drop, Gmail image loading fell by about a third in late November 2025, and some senders saw open rates drop 30% or more. Clicks and revenue didn't fall the same way, which suggests most of the drop came from fewer false opens.
Add summaries to that picture, and an "open" means less than it used to. A subscriber can read the summary, understand the offer, and decide without opening. Another can have the email opened automatically and never read it.
| Metric | What it tells you now | How much to rely on it |
|---|---|---|
| Opens | Directional trends over time, within the same audience | Low to moderate |
| Clicks | Someone acted on the email | High |
| Conversions and revenue | The email produced a result | High |
| Unsubscribes and complaints | The email or frequency missed with someone | High |
| Inactivity over time | A subscriber has drifted away | High |
The practical shift is to judge campaigns mainly by clicks and conversions, and to use opens as a rough trend line. This also matters for list management. A subscriber who hasn't clicked in six months is a more meaningful signal than one whose open rate dropped after a mailbox provider changed how it loads images.
Engagement History Decides More of What Gets Seen
There's a broader pattern behind all of these features. Inbox providers are using AI to decide what each person sees first, and the clearest input they have is how that person has treated your email before. Gmail's "most relevant" Promotions view favors brands a subscriber interacts with. Apple's priority messages lift what it judges to be important.
For senders, this means engagement history carries more weight. Subscribers who regularly click your email are more likely to see it near the top of their inbox. Subscribers who have ignored your last twenty sends are more likely to see it sorted away, summarized briefly, or not at all.
Keeping track of who is engaged, and acting on it, is the work RoblyEngage is built for. It tracks how each subscriber interacts with your email over time and flags contacts who have gone quiet, so you can focus campaigns on people who respond and run a separate win-back sequence for the rest. A list built on real engagement gives inbox providers better signals about every email you send.
Timing contributes to the same signals. RoblyAI analyzes each subscriber's email habits and delivers campaigns when that person is most likely to engage. An email that arrives while someone is actively checking their inbox has a better chance of being read in full while it's still near the top of the list.
Practical Tips for Writing in the Summary Era
- Lead with the point. Put the purpose of the email, and the offer if there is one, in the first two or three sentences.
- Use specifics. Name the product, the discount, the date, and the deadline in plain words.
- Match your preview text to your opening. Both should communicate the same main idea.
- Keep one main message per email. A focused email produces a focused summary.
- Write descriptive headings and calls to action. "Shop the winter sale" says more than "Learn more."
- Check how your emails look in Apple Mail. Send test campaigns to a device with summaries turned on and read what it says.
- Measure by clicks and conversions. Treat opens as a rough trend line.
- Protect your engagement history. Focus sends on active subscribers and re-engage the rest separately.
Bringing It Together
AI summaries change the first impression your email makes, and they make that impression depend more on the clarity of what you wrote. An email with its main point up front gets described accurately. An email with a vague opening gets described vaguely.
The same shift reaches past the summary itself. Inbox providers are increasingly deciding what each person sees based on how they've engaged before, and open rates are a weaker guide than they used to be. Clear writing, engagement-based list management, and measuring by what subscribers actually do all point in the same direction: email that's easy to understand, sent to people who want it, judged by the actions it produces.
