Email client support

MailInApp measures what each email app does with its emails in real inboxes: a test kit is mailed to each app and read there by a person, and the results decide how every block is built (latest run: October 2026). Where an app can't run a block, the block falls back instead of breaking: its content shows, and a link opens the interactive version on the web, so every reader can still answer.

Where each block works

✅ works in the email · ↪ falls back: the content shows, with a link to the web version · ❌ not supported

Not measured yet: Apple Mail on macOS, new Outlook for Windows, and Samsung Email.

Classic Outlook for Windows gets its own version of every email (see below).

How each kind of block behaves

• One-tap choices (poll votes, ratings, RSVPs, booking times) are plain links in every email app. A tap opens a short page that records the answer. Plain links are the one thing that works everywhere, which is why every MailInApp interaction has a link-based path.
• Typed answers (forms, quizzes, an assignment's answer) send from inside the email in the apps that can post a form: Gmail on the web and the Outlook apps for iOS and Android. Every form also shows an Answer on the web link underneath, so readers in other apps answer in the live view.
• Tap-to-reveal blocks (accordion, flashcards, before/after, image hotspots, the menu, scratch-off, mystery box, spin-to-win) run where the app keeps the CSS that drives them. Elsewhere nothing stays hidden: every accordion answer is open, both sides of each flashcard and both before/after pictures show, hotspots become a numbered list under the picture, the menu's links sit in one row, and the games show a Reveal my prize link (or the prize itself when the block has no prize list).
• The carousel, tabs and the image gallery switch in Mail on iOS, iCloud Mail and Thunderbird. Everywhere else the carousel shows its first slide and a "See all" link, or every slide in a grid if you choose that fallback; tabs show every tab's content under its title; the gallery shows its first picture with the others small underneath.
• Web fonts show only where the table says. Other apps use the fallback font you picked, and the preflight check lists them for your email.
• Custom dark mode (your own dark palette and dark images) applies in the apps marked ✅. Gmail on the web keeps the email light, and the other apps recolor it themselves.

The same data in the studio

This table, the studio's Where it works line on each interactive block, and the Clients preview tier all read one set of measurements, so they always agree. See Preview & test for the badges and the per-app preview.

Classic Outlook for Windows

Classic Outlook gets a dedicated version of every email: table-based layout through conditional comments, static content, countdown GIFs (with a meaningful first frame, since very old versions show only that), and live-view links for everything interactive.

Microsoft is moving classic Outlook users to the new Outlook through 2026–2027. Until that's done, both are first-class targets. Conditional comments are honoured only by classic Outlook, which makes them a safe way to target it alone.

How we measure

Each app gets the same test kit: small probes for each CSS technique the blocks use, plus every interactive block. A person reads them in the app, light and dark, and taps through. The table above comes from those runs. A new technique ships only when it falls back cleanly where it doesn't run: see How fallbacks work.