Paste the HTML — see it at desktop and phone width, get the tags Outlook and Gmail won't understand with line numbers, and the weight against Gmail's clipping limit. No signup, no limits.
Desktop Outlook on Windows renders email with the Word engine, not a browser one, and everything else follows from that: flexbox and grid are ignored, negative margins collapse, a background image on a block is not drawn without VML, and padding on a div may simply not apply. That is why reliable email markup is tables, inline styles and conditional comments for Outlook.
Markup for unsupported properties and elements, email weight against Gmail's clipping threshold, alt text and explicit sizes on images, the width of the main table, and whether there is an unsubscribe link. Everything runs in the browser: the HTML is never uploaded.
It does not render your email inside Outlook or Gmail — the preview is a browser render at 600 and 360 px. It catches the known-to-break patterns; for a pixel-exact view of each client you still need the clients themselves or a rendering service.
Take a ready template. Ours are built from MJML into the table-and-VML structure Outlook expects, and the free versions download without signup. If you're fixing your own markup, responsive email without a framework explains the fluid-hybrid layout these checks assume, and anatomy of a newsletter covers the blocks an issue is made of.
Four emails a shop actually sends, built in MJML in a 1970s ledger style: the parcel went out, here is your receipt, your seat is held, the thing you asked about is back. Warm paper, oxblood, squared corners. Built for Outlook, Gmail and Apple Mail, dark mode wired up. The dispatch email is free.
light / dark inbox · desktop and mobile
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