Each change is a dated natural experiment
Each intervention is discrete and dated, which makes each one a natural experiment a sender can measure a before-and-after against (see measuring intermediation). Most of these changes add a layer of filtering, ranking or summarisation between the sender and the recipient; most are framed by the platform as a user-protection feature. The practical upshot for a programme is that the inbox and the lock screen are moving targets on which the surviving levers are authentication, list hygiene and engagement.
Email and push interventions
| Date | Intervention | Note |
|---|---|---|
| Sep 2021 | Apple Mail Privacy Protection (iOS 15) | Image proxy inflates opens by tens of percentage points on Apple heavy lists, roughly doubling measured open rates; the Mozilla/5.0 user agent becomes the canonical proxy signature. |
| Sep 2021 | iOS 15 Focus and interruption levels | Four level taxonomy; time sensitive is the only addressable level and is not for marketing. |
| Aug 2022 | Android 13 runtime notification permission | Opt in becomes an explicit grant; opt in rates fall sharply. |
| Feb 2024 | Gmail and Yahoo bulk sender requirements | SPF, DKIM, DMARC alignment, RFC 8058 one click unsubscribe, spam rate under 0.3%. Microsoft followed May 2025; Google escalated to rejection Nov 2025. |
| Oct 2024 | iOS 18.1 Apple Intelligence notification summaries | On iPhone 15 Pro forward; the sparkle icon appears. |
| Jan 2025 | iOS 18.3 disables news and entertainment summaries | After the BBC complaint; the cleanest natural experiment for the summarisation effect. |
| Nov 2025 | Pixel notification summaries and Organizer | Pixel 9 and 10; the December follow up auto categorises and silences low priority alerts. |
| Jan 2026 | Gmail AI Overviews and AI Inbox | Powered by Gemini 3; email summarisation default on mobile in most regions. The most aggressive email intermediation since the Promotions tab. |
| early 2026 | Galaxy S26 One UI 8.5 Notification Highlights | On device summarisation on Samsung’s stack. |
| Feb 2026 | Microsoft pulls Copilot Priority View from Outlook mobile | Cost and feedback driven; Prioritize My Inbox itself continues across clients. |
Sender cooperative signals
The signals senders get back are aggregate and deliverability-focused: Gmail Postmaster Tools (aggregate spam rate and reputation by IP and domain) and Microsoft SNDS. The one proposal toward more is draft-brotman-aggregate-performance-reporting, an IETF draft (March 2026) proposing daily aggregate JSON classification and engagement reports keyed by DKIM domain. It is aggregate rather than per-message, email-only, has no summarisation hook, is voluntary for the provider and sits at an early IETF state.
The earlier intermediation layer
The summarisation panic is a thin layer on a much older story: Gmail tabs since 2013, Outlook Focused Inbox since 2016, statistical spam filtering since the early 2000s, Android notification channels since 2017 and Focus modes since 2021. A user who silenced your channel in 2019 has been a non engager for years that nobody measured.