Images in emails aren't just decoration — they're an important part of the design.But if you prepare them the wrong way, they'll end up:❌ blurry,❌ too slow to load,❌ breaking the email's layout.

In this article, we'll cover how to quickly prepare an image for an email newsletter so it looks perfect.

Step 1. Determine the image size

  • Width: no more than 600–650 px (that's the standard email width).
  • Height: not critical, but ideally no more than 400–500 px, so it doesn't take up the entire first screen.

Tip: if the image goes into a column, calculate the width relative to the column, not the whole email.

Step 2. Choose the right format

Format

When to use it

JPEG

For photos, gradients, and complex images.

PNG

For images with transparency or sharp lines (for example, logos, icons).

GIF

For animation.

⚠ Don't use SVG — it's not supported by every email client.

Step 3. Optimize the file size

  • Use services like TinyPNG or Squoosh.
  • Compress the image down to under 150 KB (ideally 50–100 KB).
  • Check that compression doesn't introduce artifacts — blurry patches, visible pixels.

Step 4. Check the resolution

  • For Retina screens, make it 2x the width (for example, if the block is 300 px, the image should be 600 px but scaled down to display at 300 px).
  • Don't insert unnecessarily oversized images.

Step 5. Add alt text

  • Write alt text so that if images are blocked, the reader still understands what was supposed to be there.

Step 6. Insert the image correctly

In the Letteros editor:

  • use the "Image" block,
  • don't set a fixed height,
  • set width to 100% with a max-width so the image adapts.

Step 7. Test the email

  • Open the preview on both desktop and mobile.
  • Check the email's loading speed.
  • Make sure the image doesn't "drift" out of the layout.

Conclusion

Preparing an image for an email is a simple but important step.Do it right, and the image will be:✔ sharp,✔ lightweight,✔ responsive,✔ and won't spoil the reader's impression of the email.

In Letteros, you can insert and check images right in the editor, and built-in tools help you avoid common mistakes.