Guide

Email Signature Testing & Debugging

How to test your email signature across different clients and fix common rendering issues.

How to test and debug your email signature across different email clients

Testing Checklist

Before rolling out your new email signature, test it in these clients:

Gmail
Web + Mobile
Outlook
Desktop + Web + Mobile
Apple Mail
macOS + iOS
Yahoo Mail
Web
Samsung Email
Android

How to Test

  1. Send to yourself: Send a test email to your own account(s) — Gmail, Outlook, Yahoo
  2. Send to a colleague: Ask them what they see on their device
  3. Check mobile: Open the test email on your phone (both iOS and Android)
  4. Check with images off: Disable image loading and see what remains visible
  5. Check reply/forward: Reply to the email and verify the signature doesn't break in the thread
  6. Check dark mode: Switch your email client to dark mode and verify readability

Common Issues & Fixes

🖼️ Broken Images

Cause: Images hosted on an expired/blocked URL. Fix: Host images on a reliable CDN or your own website. Avoid embedding base64 images.

📐 Layout Breaking in Outlook

Cause: Outlook uses Word's rendering engine, not a web browser. Fix: Use HTML tables for layout, inline CSS, avoid flexbox/grid.

📱 Too Wide on Mobile

Cause: Fixed-width tables too wide for mobile. Fix: Use max-width instead of width, keep total width under 600px.

🌙 Invisible in Dark Mode

Cause: Dark text on transparent background becomes invisible. Fix: Add background colours, use transparent-safe logo formats (PNG with padding).

↔️ Extra Spacing

Cause: Different email clients add default margins/padding. Fix: Reset margins and padding on table cells. Use cellpadding="0" cellspacing="0".

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