What Gmail and Apple Mail changes mean for marketers — Stripo.email

Email clients like Apple Mail and Gmail are quietly reshaping how your emails are previewed, opened, and engaged with. As of 2025, nearly 4.5 billion people worldwide use email, and the majority interact with it through platforms that now leverage AI-generated summaries to decide what recipients see before (or after) opening a message.

These summaries aren’t all the same. Apple Mail uses pre-open summaries — automatically written by Apple Intelligence and displayed in place of your preheader, directly in the inbox. Gmail, on the other hand, provides post-open summaries using its Gemini AI, only after the email has been opened. This difference changes everything — from how open rates are influenced to how marketers should write and structure emails.

For email marketers, this shift isn’t optional — it’s foundational. AI summaries already influence visibility, disrupt traditional messaging control, and in many cases, replace your preheader entirely. Whether your message gets opened may depend on something you didn’t write.

We’ll explain how these summaries work in Apple Mail and Gmail, what they replace, when they show up, and how you can adapt your strategy to stay visible and effective in AI-driven inboxes. We’ve also included real-world tests, screenshots, and expert insights from Dhrupalsinh Barad and Susmit Panda, who shared how these AI changes are already impacting campaign planning.

How AI summaries are generated

Gmail is gradually rolling out AI-generated post-open summaries, powered by its Gemini AI model. Unlike Apple’s pre-open summaries, Gmail’s version does not affect what recipients see in the inbox preview — instead, it helps them better understand email content after they’ve already opened it.

These summaries are most commonly available in the Promotions and Updates tabs. They’re designed to make long or cluttered emails easier to digest. Because they appear post-open, they don’t directly impact the subject line, preheader, or open rate.

Underlying technology

Gmail’s summaries are generated using Google’s Gemini LLM (large language model), which parses your email content in the background. It analyzes structured and semi-structured elements — like promotional offers, product details, calendar dates, and even support messages — and then composes a short natural-language summary that highlights the key points.

Recipients with eligible accounts (Workspace or Gemini Premium) can manually trigger this summary by clicking the “Summarize this email” button in the Gmail interface. In some cases, Google may also surface summaries automatically, especially for longer promotional messages.

The “Ask Gemini” button in Gmail opens AI-powered tools like email summarization. This feature is gradually rolling out and may appear in different places depending on your account type and region.

These summaries might appear in:

• the Gemini sidebar (desktop only);
• the email view, after you open a message;
• Gmail’s search results, when AI-enhanced snippets are enabled.

Again, these summaries are only visible after opening, which means they do not influence whether the email is opened in the first place.

Functionality and user interface

Gmail’s summaries live in the Gemini sidebar, alongside other generative tools like “List Action Items” and “Help Me Understand.” This feature is only available to Workspace users with Gemini enabled, or select users on paid Gmail tiers.

• in the inbox view, Gmail continues to show the subject line and preheader as usual;
• in the Promotions tab, Gmail sometimes formats the email preview with AI-enhanced visual layouts, but these do not contain Gemini summaries;
• in the mobile app, AI summaries may passively influence how the email is rendered, but there’s no manual summary option via Gemini on mobile at this time.

The “Ask Gemini” button in Gmail opens AI-powered tools like email summarization. This feature is gradually rolling out and may appear in different places depending on your account type and region.

In short, it’s a machine-written TL;DR (Too Long; Didn’t Read) — and it’s already rewriting how subscribers scan your content.

Apple Mail: Pre-open summaries via Apple Intelligence

Unlike Gmail, Apple Mail on iOS 18 and macOS Sonoma 14.4+ introduces pre-open summaries generated using Apple Intelligence (Apple’s on-device AI engine). These summaries appear directly in the inbox, replacing the preheader for users with supported devices, before the message is opened.

That means Apple’s summaries do influence open rates, user perception, and engagement.

Where Apple’s summaries appear:

• inbox view in Apple Mail (iPhone 15/16, M-series Macs);
• across all tabs and folders (not limited to Promotions);
• automatically, with no sender control or summary trigger.

How they work:

Apple’s AI generates short, context-aware descriptions of your email based on the content inside, often prioritizing actionable or personalized details. Summaries are built directly on the device, protecting user privacy while delivering faster previews.

What AI summaries actually replace

AI-generated summaries are beginning to disrupt how marketers present their messages in the inbox, but what they replace depends entirely on the platform.

Apple Mail: Replaces the preheader

On supported Apple devices (iPhone 15/16, macOS Sonoma), Apple Intelligence automatically generates pre-open summaries that replace your preheader text, even if you wrote one. These summaries are created using Apple’s on-device AI and are displayed directly in the inbox, below the subject line.

For marketers, this changes the inbox formula:

Old logic: Subject Line + Preheader = Engagement Strategy
New reality: Subject Line + AI Summary = Unpredictable Inbox Message

What’s shown might not be your carefully crafted teaser or brand voice — it could be a sentence rewritten by Apple’s AI based on what it perceives to be the most relevant part of your email.

That means if the AI doesn’t understand your intent, it might surface a dry confirmation line or service info instead of your hook. As a result, open rates and brand storytelling are directly affected.

Gmail: Does not replace the preheader

Gmail’s AI summaries are post-open, meaning they do not replace the subject line or preheader at all. Instead, Gmail continues to display the content you set (subject + preheader) in the inbox, as usual.

The AI summary only appears:

• after the recipient opens the message (via Gemini sidebar);
• in search results or promotional formats (when available).

So while Gmail summaries help with reading or searching content, they don’t interfere with your email’s entry point in the same way Apple does.

What this means for email structure

Even though only Apple replaces the preheader, both platforms are forcing marketers to rethink how they organize email content.

• on Apple: front-load meaningful copy, because it might become your inbox preview;
• on Gmail: front-load meaningful copy, because it could become the Gemini summary.

Either way, you can no longer rely on subject + preheader to carry your message. Your first 100–200 characters of email body should now be treated as inbox-critical content.

When and where recipients see AI summaries

AI summaries don’t appear uniformly across all inbox views, and their behavior differs significantly between Apple Mail and Gmail. Understanding where and when they appear is essential to avoid misaligned expectations and optimize your strategy for real inbox scenarios.

Gmail: Post-open only (for now)

Gmail is gradually rolling out post-open summaries, powered by its Gemini large language model (LLM). These summaries do not affect what recipients see in the inbox (e.g., subject line or preheader). Instead, they appear after the email is opened to help recipients quickly understand the content, especially in long or complex messages.

Where Gmail’s summaries appear:

• in the Gemini sidebar on desktop (via “Summarize this email”);
• sometimes, in search results when using Gemini-enhanced search;
• occasionally in Promotions or Updates tabs (visually styled, not true Gemini summaries).

Gmail occasionally formats emails in the Promotions tab with enhanced visuals or structured cards using markup, but this is not the same as Gemini-powered summaries. These are layout-based annotations, not AI-generated text.

Officially, these features are available to Workspace accounts with Gemini enabled or Gmail Premium users.

Unofficially, however, some users have reported spotting the “Summarize this email” button even on free personal Gmail accounts, suggesting a gradual or experimental rollout is underway. Google has not yet confirmed this publicly.

How they work:

Gmail’s backend parses your HTML content using Gemini, identifies key elements (offers, dates, terms), and generates a short TL;DR-style summary. This is most helpful for long promotional or transactional emails. Users with eligible accounts can manually trigger the summary or see it automatically on certain messages.

“Happening Soon” section experiments

Gmail is testing a new feature called “Happening Soon”, which surfaces structured data (like events, deliveries, or bills) in a visual module. This feature is still experimental and tied to emails that contain recognizable schema markup and structured content.

For now, it’s limited to:

• Gmail desktop/web UI;
• emails with strong date/time elements and schema.

If adopted more broadly, this could give eCommerce, event, and SaaS emails bonus visibility, but only when structured correctly.

Gmail AI in search results

Gmail offers two types of search with very different behavior:

1. Gemini-powered search (AI Summary Matching)

AI summaries may appear in Gmail’s search results if Gemini is enabled. This is different from a standard keyword search.

• with Gemini, Gmail can semantically analyze your inbox and display AI-generated snippets that summarize matching content;
• this is not available without Gemini access or on mobile browsers.

If you use the Gemini sidebar to ask something like:

“Find all webinars on email personalization this year.”
The AI returns highly specific matches (e.g., 1 email from 2025), using LLM’s understanding of meaning and time.

2. Standard Gmail search console

A regular keyword search like “email personalization webinars” shows all matches, even partial or irrelevant ones. It uses basic keyword logic — not semantic analysis — and doesn’t generate summaries.

This advanced summary-based search only works with Gemini enabled and is not yet standard across all Gmail accounts.

TL;DR (Too long; didn’t read)

• Gmail summaries: Post-open only; appear in Gemini and search; do not impact preheaders (yet);
• Apple summaries: Pre-open; replace preheaders; impact visibility and open rates;
• search behavior: Gemini’s AI search provides contextual results with summaries; standard search does not.

Feature	Gmail (Gemini)	Apple Mail (Apple Intelligence)
Summary type	Post-open (after click)	Pre-open (before click)
Appears in	Gemini sidebar, search	Inbox preview (preheader area)
Affects open rate?	❌ No	✅ Yes
Manual trigger?	✅ Yes (on desktop)	❌ No (automatic)
Available to	Workspace/Gemini users	iOS 18, macOS Sonoma users

Where Gmail’s AI summaries actually work: Platform availability and limitations

Gmail’s AI summaries are not available everywhere — or to everyone — but that’s quickly changing. Whether you’re crafting emails for desktop or mobile, Workspace users or personal Gmail accounts, knowing where AI summaries appear (and how) is essential for writing and formatting effectively.

Supported platforms

Gmail web (Desktop)

AI summaries are fully supported in the desktop version of Gmail for users with:

• Google Workspace (with Gemini enabled);
• Google One AI Premium subscription.

In this setup:

• the “Summarize this email” button appears in the Gemini sidebar after opening an email;
• summaries can be triggered manually or appear automatically in some search results;
• the feature works best in Google Chrome or Chromium-based browsers (e.g., Edge, Brave).

Gmail mobile app (Android & iOS)

As of May 18, 2025, AI summaries have unexpectedly appeared in free personal Gmail accounts on mobile, even though Google has yet to issue an official statement on this.

Here’s what we know:

• the “Summarize this email” button now appears on opened HTML emails in the Gmail mobile app (screenshot confirmed);
• this applies to both Workspace and free Gmail users, without requiring a premium plan;
• there is still no Gemini sidebar on mobile, just a single summarization action button.

While not listed on Google’s support page, this rollout seems to be live for many users and could expand further.

Apple Mail: Pre-open summaries (and inbox impact)

In contrast, Apple Mail uses AI to generate summaries that replace the preheader text directly in the inbox, before the recipient opens the message.

Supported on:

• iPhone 15/16 (all models, iOS 17+);
• macOS Sonoma 14.4.1+.

These summaries influence the open rate because they act as part of the message preview. Marketers cannot override or disable them, and even well-written preheaders may be ignored.

Limited or unsupported environments

While Gmail’s AI summaries are steadily expanding, not all users or setups have full access, especially when it comes to manually triggering summaries or using advanced Gemini tools. Here’s where functionality remains limited, inconsistent, or unavailable.

Standard Gmail accounts (free/non-workspace)

Until recently, personal Gmail users couldn’t access Gemini or trigger summaries manually. However, as of May 18, 2025, many free accounts have started seeing the “Summarize this email” button, at least for HTML emails, even without a Google One AI Premium subscription.

That said, functionality is still more limited compared to Workspace or Gemini-enabled accounts:

• no Gemini sidebar on desktop;
• no guaranteed access across all devices or email types;
• feature may be rolling out gradually and inconsistently.

In short, basic summarization might now work, but full control still requires an upgrade.

Mobile browser (Chrome/Safari on phones)

The mobile web version of Gmail remains the most restricted:

• no Gemini integration;
• no summarize button;
• no support for advanced formatting previews.

If users want access to AI summaries, they must use the Gmail mobile app, not the browser version.

Google Workspace without Gemini enabled

Even if your organization uses Google Workspace, Gemini features must be explicitly enabled by your Workspace admin or purchased via an eligible plan.

Without this:

• you won’t see the “Ask Gemini” button;
• summarization tools remain locked;
• inbox previews rely only on traditional metadata (subject + preheader).

Non-Chrome browsers (Safari, Firefox, etc.)

Gmail is technically functional in non-Chrome browsers, but Gemini-powered summaries are often limited or broken:

• sidebar may fail to load;
• “Summarize this email” button may not appear;
• AI-generated interactions may be inconsistent.

For the best compatibility, Google Chrome is still recommended.

Platform summary table

Platform	Summary visible	Manual summary (Gemini)	Notes
Gmail Web (Chrome)	✅ Yes	✅ Yes	Full functionality if Gemini is enabled
Gmail App (Android/iOS)	✅ (HTML emails)	✅ Yes	Works even on free accounts for HTML emails
Gmail Web (Firefox/Safari)	⚠️ Partial	❌ No	Limited or buggy Gemini tools
Gmail Mobile Browser	❌ No	❌ No	Gemini is not supported in mobile browser versions
Gmail (Free Accounts)	⚠️ Partial	✅ (in some cases)	Rollout has begun, but not consistently available yet
Workspace without Gemini	⚠️ Previews only	❌ No	Needs admin activation or AI Premium plan

Implications for email marketing

AI-generated summaries aren’t just a minor UX upgrade — they’re reshaping how your emails are interpreted, surfaced, and prioritized in the inbox. But not all AI summaries function the same way, and that distinction is critical for marketers.

Currently, there are two types of AI-generated summaries:

• pre-open summaries (used by Apple Mail on iOS/macOS) appear before the recipient opens the message. These can replace the preheader and directly impact open rates;
• post-open summaries (like those in Gmail) are generated after opening the email or manually triggered via Gemini. They do not replace the preheader in the inbox preview — so while they influence how recipients process emails once opened, they don’t affect open rates themselves.

Still, both forms bring important strategic shifts.

Reduced control over messaging

In traditional email workflows, marketers could control almost everything a recipient saw in the inbox: the subject line, the preheader, formatting, and even emoji placement.

But with AI stepping in — especially on Apple Mail, where summaries appear in place of preheaders — that control is eroding. The AI might display a completely different line from your email, and you’ll have no say in what it chooses.

That could mean:

• losing the punchline of a teaser subject line;
• spoiling exclusive deals too early;
• showing irrelevant or outdated content.

For Gmail users, the story is slightly different. Summaries don’t replace inbox previews — they appear after the email is opened or are surfaced in Gemini. But that doesn’t mean they’re harmless. If Gmail’s AI chooses a poorly written or out-of-context sentence, it can still color how your email is perceived, even after a successful open.

Potential for misinterpretation

Both Gmail and Apple’s AI systems are language models, not marketers. That means they can misunderstand intent, miss the most important points, or extract text that’s entirely out of context.

Common risks include:

• summaries generated from legal disclaimers or unsubscribe lines;
• highlighting shipping policies instead of product announcements;
• repeating phrases like “Hello there!” or “This email contains…”

These misfires don’t just look awkward — they can harm engagement by confusing readers or weakening the perceived value of the message. This is especially problematic for pre-open summaries in Apple Mail, where recipients might decide not to open based on that single line.

Impact on open rates

Let’s be clear: only Apple’s pre-open summaries currently affect open rates directly. Since they replace or override the preheader in the inbox, they’re part of the decision-making real estate alongside the subject line.

This means your traditional subject line + preheader combo is no longer reliable in Apple Mail. If the AI pulls something bland, irrelevant, or vague, your open rate could take a hit, especially among younger recipients who tend to skim quickly.

Gmail’s post-open summaries, on the other hand, appear only after the email is opened or through Gemini’s sidebar. While they don’t affect open rates, they do shape recipient perception after the click, making them critical for engagement, comprehension, and conversion.

• assume less control over what recipients  see first, especially on Apple devices;
• don’t rely on preheaders alone. Design your email’s opening lines to stand on their own;
• structure content clearly so both AI and humans can extract the right meaning;
• test across devices to see how AI behaves in real-world inboxes.

AI summaries are becoming part of the inbox landscape — whether we like it or not. Smart marketers will adapt early and shape their strategies around this new layer of interpretation.

Strategies for marketers to adapt

With AI-generated summaries now part of the inbox experience in both Gmail and Apple Mail, email marketers need to rethink how they structure their content. While you can’t directly control what the AI shows, you can influence it and stack the odds in your favor across both platforms.

The key? Build your emails with summarization in mind from the very first word.

Front-load key information

Whether you’re targeting Gmail or Apple users, the top lines of your email body now matter more than ever. For Apple Mail, the summary is shown in the inbox before recipients open the email. For Gmail, the summary is generated after opening (or manually via Gemini), but that still affects engagement and how the message is interpreted.

Actionable tips:

• start with your most important value proposition within the first 100–200 characters;
• avoid fluffy intros like “Hey there” or vague lead-ins;
• assume the first sentence may be reused — even if you didn’t plan for it.

Think of your opening like a social post caption: short, clear, high-impact.

Use clear and structured formatting

AI systems need visual cues to identify what matters. The more structure you give your content, the easier it is for both humans and AI to scan and summarize it correctly.

Best practices:

• use headings, subheadings, and bullet points to break up content;
• bold key lines or CTAs to signal importance;
• avoid large image blocks with no surrounding text, especially at the top.

Clean structure improves readability in Apple Mail. In Gmail, it helps Gemini understand and extract the right context for post-open summaries.

Test and optimize with AI in mind

AI doesn’t always behave consistently across devices or inbox types, which means testing is non-negotiable.

What to test:

• A/B subject line + body combinations (not just preheaders);
• HTML vs. plain-text fallback quality;
• summary visibility across Gmail (Workspace vs. personal), Apple Mail, mobile, and desktop.

If you’re using Gmail, note that the EmailMessage schema may help gently nudge what gets summarized, though it’s not a guarantee. And if you’re in Apple’s ecosystem, structure and clarity will always beat cleverness.

When Gmail is most likely to summarize

Gmail tends to trigger AI-generated summaries when:

• the preheader is missing, repetitive, or generic;
• the top of the email is image-heavy with little text;
• the sender uses structured data (e.g., EmailMessage schema);
• the email lands in the Promotions tab.

So if you want Gmail’s AI to summarize the right thing, make sure your HTML is clean, readable, and logically organized.

You can’t stop Gmail or Apple from summarizing your emails. But with a few smart formatting decisions and strategic copy placement, you can guide what they show — and protect the story you’re trying to tell.

Wrapping up

AI-generated summaries in inboxes are no longer experimental — they’re here, and they’re redefining how your emails are seen, scanned, and judged. Whether it’s Apple’s pre-open summaries that replace your preheader in the inbox, or Gmail’s post-open Gemini summaries that shape engagement after the click, AI is quietly taking over the front lines of email communication.

For marketers, this means shifting away from the illusion of full control. It’s no longer just about writing a strong subject line or designing the perfect hero image. It’s about structuring your email content to work with the AI, not against it.

You can’t choose what Gmail or Apple shows — but you can influence it:

• front-load essential info;
• avoid vague or misleading intros;
• use clear formatting and hierarchy;
• test your emails across inboxes and clients.

AI-driven inboxes are becoming the new normal, and with platforms like Gmail and Apple Mail dominating the market, learning to optimize for both is no longer optional.

This isn’t the end of human-crafted email strategy. It’s the evolution of it. One where your opening lines, formatting decisions, and structure now do just as much work as your subject line ever did.