Basic Clean Letter

It opens: "My Company Slogan here Promotion My Awesome Text Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin rutrum enim eget magna efficitur, eu semper augue semper. Aliquam erat volutpat. Cras id dui lectus. Vestibulum sed finibus lectus, sit amet suscipit...". Links: "Promotion", "Learn more". 4 images, 29 Outlook-only blocks, no dark-mode query, web font.

The spread is what matters on this template: 100 in Apple Mail against 55 in Outlook Classic, a 45-point gap across the same file. 1 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 216 warnings behind that score are concentrated there rather than spread evenly.

At 20.9KB compiled it has roughly 81KB 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 reference numbers, amounts and support link. Transactional mail is read for its data, so put the value the reader came for in the first block rather than below a banner.

Leave alone: The table scaffolding around the detail rows. Outlook derives row height from cell padding and ignores margins entirely, so swapping the tables for divs is what turns a tidy receipt into a stack of touching lines.

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