The 5 design rules every email signature should follow in 2026
Stop using stretched logos and 12-pt Comic Sans. Here's the short list of rules our designers apply to every signature we ship.
Mira Okafor
· Lead designer ·
May 16, 2026
·
5 min read
Why most signatures look bad
A signature is the last thing your reader sees before they decide whether to reply, ignore, or unsubscribe. And yet, almost every signature we audit suffers from the same handful of issues — too many fonts, stretched logos, social icons that don't click, and stray underlines from Outlook.
Rule 1 — Tables. Always tables.
Modern email clients still don't render flexbox or grid reliably. We use semantic HTML tables with inline styles for every signature we build. It looks old-school, but it's the difference between something that renders cleanly in Outlook 2019 and something that arrives as a broken pile of inline images.
Rule 2 — One font, one accent colour
You don't need three typefaces to look like a brand. We pick a single web-safe sans-serif and pair it with one accent colour drawn from the customer's brand palette.
Rule 3 — Photos as round PNGs, never JPGs
PNG with transparency renders consistently across light and dark mode. JPGs blow out in Apple Mail dark mode and add white halos.
Rule 4 — Tap targets, not just text
Every link in your signature should be at least 36px tall on mobile. We wrap social icons in 40px clickable boxes — the difference is night and day on iPhone.
Rule 5 — Test in Outlook 2019 dark mode
Outlook 2019 on Windows is the worst-behaving major email client. If your signature passes Outlook 2019 dark mode, it passes everywhere.
