Outlook and Gmail are the two most popular email clients in Australia, but they handle signatures very differently. Understanding these differences will save you time and frustration when setting up your email signature.
The Fundamental Difference
Outlook stores signatures as local files on your computer (or synced via Microsoft 365). You can have multiple signatures and switch between them per email.
Gmail stores signatures on Google's servers and applies them automatically. You can create multiple signatures but must set a default — it's more "set and forget."
HTML Rendering Differences
This is where things get tricky. Both clients support HTML signatures, but they render them differently:
| Feature | Outlook | Gmail |
|---|---|---|
| Table layouts | ✅ Full support | ✅ Full support |
| Inline CSS | ✅ Full support | ✅ Full support |
| External CSS / <style> tags | ⚠️ Partial | ❌ Stripped out |
| Web fonts | ❌ Falls back to system | ❌ Falls back to system |
| Embedded images | ✅ CID attachments | ⚠️ Converted to base64 or linked |
| Max signature size | No hard limit | ~10,000 characters |
| Multiple signatures | ✅ Unlimited | ✅ Up to 5 (Workspace unlimited) |
Image Handling
This is the #1 source of signature headaches:
- Outlook embeds images as CID (Content-ID) attachments by default. This means your logo travels with every email, increasing file size. Recipients often see "1 attachment" even though it's just your logo.
- Gmail can reference externally hosted images (URLs) or convert pasted images to base64. Hosted images are better — they keep your email small and load quickly.
Best practice: Always use externally hosted images (URLs) in your signature. This works reliably in both Outlook and Gmail and avoids the "phantom attachment" problem.
Setup Process
Outlook Setup
- Open Outlook → File → Options → Mail → Signatures
- Click "New" and name your signature
- Paste your HTML signature into the editor
- Set as default for new messages and/or replies
Full guide: How to Add an Email Signature in Outlook →
Gmail Setup
- Open Gmail → Settings (gear icon) → See all settings
- Scroll to "Signature" section
- Click "Create new" and paste your HTML signature
- Set as default for new emails and/or replies
Full guide: How to Add an Email Signature in Gmail →
Which Is Better for Signatures?
Neither is objectively "better" — they're just different. The key is to design your signature to work in both. That means:
- Use table-based layouts (not divs or flexbox)
- Use inline CSS only (no <style> blocks)
- Use web-safe fonts (Arial, Helvetica, Georgia)
- Host images externally via URL
- Keep the total HTML under 10,000 characters for Gmail compatibility
💡 Good news: All 132 of our email signature templates are built with cross-client compatibility in mind. They use table layouts, inline CSS, and hosted images — so they look great in both Outlook and Gmail out of the box.