Short answer:
Keep all email signature images under 300 KB and within 800 px to ensure fast loading, reliable display, and better email deliverability.
At Xink, our goal is to ensure your email signatures always look professional and load quickly—no matter where your emails are viewed.
To support this, we enforce a 300 KB maximum file size and a maximum width of 800 px per image. These limits help ensure consistent rendering across email clients while reducing the risk of emails being flagged or delayed.
How to optimise email signature images
You can quickly optimise images using tools like:
Important: Do not upload large or print-sized images and rely on HTML to scale them down. Always resize images before uploading.
Resize first
Reducing image dimensions often decreases file size significantly before compression is applied.Choose the correct format
- PNG: Best for logos, icons, and graphics with flat colours
- JPEG: Best for photos and complex images (use 60–80% quality)
Compress the image
- Resize to the correct pixel dimensions
- Export for screen/web (not print)
- Adjust quality to reduce file size without visible loss
Keep file size low
Aim to keep each image well below 300 KB. Most signature images can be reduced to under 100 KB.Test before publishing
- Add the image to your Xink signature
- Send a test email
- Check on desktop and mobile devices
- Review in both light and dark mode
If the image looks sharp and loads instantly, the optimisation is successful.
Why the 300 KB and 800 px limits matter
✔ Protects email deliverability
Large images increase email size and can trigger spam filters. Keeping images under 300 KB improves inbox placement.
✔ Reduces email size
Signature images are included in every reply and forward. Large files can:
- Slow down email loading
- Increase thread size
- Cause issues in long conversations
✔ Saves storage and bandwidth
Email signatures are stored repeatedly across mail systems. Optimised images:
- Reduce storage usage
- Lower bandwidth consumption
- Improve performance on mobile and slower connections
Recommended image dimensions
Use the following guidelines when designing email signature images:
- Horizontal logo: 250–400 px wide
- Square/stacked logo: 150–300 px high
- Banner: 600–800 px wide
- Headshot: ~100 px wide
- Social icons: 24–48 px (square)
Staying within these dimensions helps keep images sharp while making it easier to stay below the 300 KB limit.
There is no strict height limit, but shorter signatures provide a better experience—especially in long email threads.
