At Xink, our goal is to ensure your email signatures always look professional and load instantly—no matter where your emails are viewed. We enforce a 300KB maximum file size and an 800px dimension per image within signatures, ensuring your emails load quickly, display correctly, and avoid being flagged as spam.
Why the 300 KB & 800 px Limit Matters
✔ Protects email deliverability
Oversized images can increase the weight of a message, raising spam scores or triggering security filters. Keeping each image under 300 KB helps your emails reach the inbox more reliably.
✔ Reduces overall email size
Every signature image is sent repeatedly in every email and reply. Large images quickly bloat long threads and can cause:
- Slower load times for recipients
- Issues with mailbox size limits
- Problems when forwarding or replying to long conversations
✔ Saves storage & bandwidth
Email archives store signatures millions of times. Optimised images:
- Reduce long-term storage costs
- Lower bandwidth usage for your organisation
- Improve performance for users on slow or mobile connections
Recommended Image Dimensions for Email Signatures
As a general guideline for email signatures:
- Horizontal logo: 250–400 px wide
- Square/stacked logo: 150–300 px high
- Banner: 600–800 px wide
- Headshot: 100 px wide (approximately)
- Social icons: 24–48 px (square)
Staying within these ranges ensures your images remain sharp on screen while remaining safely below the 800px limit, making it easier to keep under 300 KB. There is no height limit for email signatures, but recipients don’t want to keep scrolling through a long signature, especially in an email chain.
How to Optimise Email Signature Images
Always resize your image before you compress it.
Remember: Resizing alone can often dramatically reduce the file size, even before compression. Do not upload print-sized or huge photos and rely on HTML to shrink them visually.
Resizing alone often reduces the file size dramatically, even before compression.
- Choose the correct format. Pick the image format that matches your content:
- PNG: Best for logos, flat colours, text, and simple graphics.
- JPEG: Best for photos and complex images; export at 60–80% quality.
- Compress smartly. Use your preferred image editor or any reputable online optimisation tool to:
- Resize to the correct pixel dimensions (if not already done).
- Export for screen/web, not for print (72–96 dpi is enough for email).
- Adjust quality until you achieve a small file size without apparent visual degradation.
- Aim to keep each image well under 300 KB. Most correctly sized signature graphics can be reduced to well below 100 KB.
- Test at real size. Always test your optimised images in context:
- Insert the image into your Xink email signature.
- Send a test email to yourself and colleagues.
- Check the signature on desktop and mobile email clients.
- If possible, review in both light and dark modes.
If the image looks crisp at its actual size and the email loads quickly, your optimisation is successful.
