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Feature Announcement · Protocol

Overall compatibility: 96/100 across 21 email clients · 20 of 21 clients passing (6 clean at 100%) · 169 compatibility warnings (0 error-level) · 24.3KB compiled HTML.

Cross-client fidelity Tested against 21 email clients. 6 of 21 clients render cleanly with 100% fidelity. Only Outlook Classic has reduced fidelity (70/100) due to legacy desktop engine constraints.
email://preview/ protocol-feature-announcement.html
RE

Attribution · React Email

Template adapted from the open-source React Email collection under the MIT License (© Plus Five Five, Inc. / Resend). Full React source code is included.

Client Compatibility

Score: 96/100 · 20/21 passing

21 clients tested
6 of 21 clients render with 100% fidelity. Lowest is 70/100 in Outlook Classic due to legacy desktop styling limitations.

Notes on this template

It opens: "Meet a new way to manage work Introducing Smart Tasks : a calmer way to organize work, surface what matters next, and keep your team aligned without the noise. Explore Smart Tasks Meet smart tasks Auto-prioritization All your tasks for...". Preheader: "Meet Smart Tasks". Links: "Help Center". 11 images, 4 Outlook-only blocks, no dark-mode query, web font.

The spread is what matters on this template: 100 in Superhuman against 70 in Outlook Classic, a 30-point gap across the same file. 6 of the 21 clients render it without a single flagged property. Outlook Classic is the one to preview against after any edit, because it is where this template has the least margin, and the 169 warnings behind that score are concentrated there rather than spread evenly.

At 24.3KB compiled it has roughly 78KB of headroom before Gmail clips the message at 102KB and hides the rest behind a "View entire message" link. Inlined CSS and base64 images both count toward that, so watch it as you add sections.

Safe to customise: The screenshots and the walkthrough copy. This is the longest thing most products send, which makes total size the constraint to watch rather than layout.

Leave alone: The heading hierarchy. It carries the outline screen readers announce, and flattening headings into styled text is the most common accessibility regression in announcement mail.

Modified it? Check your version against the same 21 clients.

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