Apple Mail and Gmail overwrite the preheader with AI summaries
Apple Intelligence is on by default on compatible iPhones, iPads and Macs. In the Mail app that means: where the preheader used to sit — the first characters visible after the subject line in the inbox list — there is now an AI-generated summary. Google is rolling out the same mechanism with Gemini in Gmail’s web and Android apps, gradually. For email marketing teams that have spent years carefully crafting preheader texts, that is a quiet break.
What actually changed
- Apple Mail overwrites the preheader on iOS devices with Apple Intelligence (default-on for compatible hardware). This applies to the inbox list, not just to the opened mail.
- Gmail rolls out Gemini summaries for Workspace accounts, optionally with admin opt-out.
- What the AI summarises is the mail body — not the hidden preheader text. The CSS-hidden preheader string that was the open-rate lever for years is gone as a signal.
- The first 100–200 characters of the body are the new inbox-critical zone. They decide what the summary says.
What used to apply
The preheader was one of the few direct levers for the inbox view. Classic setup: a hidden HTML line at the start of the mail (<div style="display:none">…</div>) with a teaser that meaningfully extends the subject. Mail clients displayed exactly that text in the inbox list — Apple Mail, Gmail, Outlook alike. Anyone who ran A/B tests with preheader variants measured relevant open-rate movements there.
The game was simple: subject is the hook, preheader is the second stimulus. Both sender-controlled, both steerable via template.
What applies now
1. On Apple devices with Apple Intelligence the preheader is invisible. Apple Intelligence has been on by default since iOS 18.2 / iPadOS 18.2 / macOS 15.2 on compatible hardware (iPhone 15 Pro and newer, M-series Macs, iPads from M1 onwards). The inbox list shows the AI summary under the subject instead of the preheader. The hidden preheader text from the template is no longer considered — Apple Intelligence reads the visible mail body and distils a summary from it. Recipients without Apple-Intelligence hardware still see the preheader; the share of affected recipients grows with every hardware generation.
2. Gmail follows with Gemini summaries. Currently mainly rolled out in Workspace accounts, optionally in the mobile app. Unlike Apple, the Gemini summary is not consistently inbox-prominent but often appears as a “Show AI summary” button inside the opened mail. But: where Gemini kicks in, the same logic applies — the first sentences of the body shape the impression, not the preheader.
3. Sender control shifts from the preheader to the first body paragraph. This is not just cosmetic. The first body paragraph used to be part of the mail, written for the recipient after opening. Now it is also the inbox teaser, read by an AI that summarises. The requirement on the first paragraph changes accordingly: it must make clear in two sentences what it is about and why it is relevant — otherwise the AI will produce a summary that the sender will not be happy with.
Why barely anyone noticed
Apple Intelligence was communicated as the “Apple AI story”, not as the “email marketing story”. The Mail app changes are in the Apple support article, but no Apple keynote slide said “bye bye preheader”. On top of that: anyone with Apple Intelligence active on their own device sees the slick summary in the inbox — and does not necessarily think that recipients of their own newsletter see the same thing.
On the Gmail side Gemini runs unobtrusively in the inbox, often hidden behind a click. The impact is therefore smaller today than with Apple, but the pattern is clear: the more inbox providers put their own AI in front of human perception, the less sender-controlled micro-optimisation on the subject/preheader pair counts.
What to do now
Write the first body paragraph like a preheader: Two sentences that make promise and content clear. Concrete nouns, no marketing fluff. If the recipient already knows after these two sentences whether it is relevant, the AI summary will work in your favour too.
Don’t pull the hidden preheader out yet. It still works for all recipients without Apple Intelligence and in many Outlook/web clients. But stop treating it as the primary lever — the primary lever is now the first body paragraph.
Test with an Apple-Intelligence device: Send your newsletter test-wise to a mailbox you have set up on a current iPhone, and look at what Apple Intelligence makes of your mail. That is the most honest inbox check you can get today — and usually very revealing.
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