Our users read our emails on a device we stopped designing for.

We analyzed email opens across 4.1 million sends over 12 months.

Opened on desktop: 31%
Opened on mobile: 52%
Opened on tablet: 9%
Opened on unknown/other: 8%

Our email templates were designed on desktop, tested on desktop, and approved on desktop. 52% of opens happened on a phone, where our two-column layout collapsed into a single unreadable column and our 14px font became 8px of squinting.

We rebuilt every template mobile-first. Click-through rate on mobile rose from 6.2% to 14.1%. Desktop click-through stayed flat, because the desktop version was already fine.

The device you design on is not the device your message is read on. What are you designing on, and what are your users actually holding?