Your email on a phone
Most email is read on a phone. Designing for the wide screen first is designing for the minority.
One column
Two- and three-column layouts break or become unreadable. One column works everywhere, including on a wide screen.
Buttons big enough
A text link is hard to hit accurately. A real button with space around it prevents missed taps and frustration.
Readable text
Too small forces zooming, and most people give up before that. Be generous with font size.
The most important thing at the top
On a phone you see a third of what fits on a computer. Your main message and your button must be visible without scrolling.
Light images
Your recipient may be on the move on a slow connection. A two-megabyte image is never seen.
