Image Optimisation for Email Campaigns

Email has unique constraints: mobile data, old email clients, limited CSS support. Image optimization for email differs significantly from web.

File Size Limits

Many email providers limit total message size to 25MB. Heavy images trigger spam filters. Keep images under 100KB each.

Format Choice

JPEG or PNG only. WebP, AVIF, GIF animation are not reliably supported in email clients. Use JPEG for photos, PNG for graphics.

Resolution

Email clients resize images to 600px wide on desktop, 320px on mobile. Prepare images at these sizes. Oversized images are scaled down by clients anyway.

Compression

Use aggressive JPEG compression (75–80% quality). Mobile data is slow. Users will not wait for large email images. Optimize for fast rendering over bandwidth efficiency.

Alt Text

Always provide alt text. Email clients block images by default. Alt text is the fallback for 50% of email opens.

Color Space

Use sRGB only. Wider color spaces are not supported in email.

Transparent PNGs

PNG transparency works in modern email clients but not in Outlook 2007-2019. Use JPEG + solid background color as fallback.

Test Across Clients

Email rendering is fragmented. Test in Gmail, Outlook, Apple Mail, mobile clients. Some render images differently.

Optimization Workflow

Resize images to 600px, optimize to 80KB JPEG, provide alt text, test across clients. QuickConvert's batch tool handles resizing and JPEG optimization.