Building Emails
Images, and reading well on a phone
Practical rules for images in email, and the checks worth doing before every send.
Last updated September 2, 2026
Most of your campaign is read on a phone, often with images switched off, sometimes in dark mode. Designing for that is the difference between a campaign that works and one that looks fine on your desktop only.
Images
- Never put your message in a picture. Many mail clients block images by default; a text-in-image email arrives blank.
- Keep them a sensible size. A ten megabyte photo is slow on mobile data and can trip spam filters.
- Add alt text so there is something to read while images are blocked.
- Do not rely on a background image — support is patchy and it often just does not appear.
Dark mode
Many phones invert email colours. A logo saved as black text on a transparent background disappears entirely against a dark card. Use a version with a solid background, or one that works both ways.
The pre-send check
- Send a test to yourself.
- Open it on a phone. Is the main message visible without scrolling or pinching?
- Turn images off, or look at it before they load. Does it still make sense?
- Check every link goes where you think.
- Read the subject line once more — it is the only part most people will ever see.
THE FIVE MINUTES THAT SAVE THE CAMPAIGN
A broken link found in a test costs nothing. The same link found after ten thousand sends cannot be fixed at all.