Outlook Software Strips Out Inline CSS in Emails: A Developer's Guide to Email Compatibility

As developers crafting HTML emails, one of the most frustrating challenges is achieving cross-client consistency. We design layouts that look perfect in Gmail, Apple Mail, and modern web browsers, but often encounter a hostile environment when deploying to legacy clients like Microsoft Outlook. The specific issue you’ve encountered—where inline CSS properties, especially those controlling dimensions on images, vanish in Outlook—is a classic symptom of these rendering engine differences.

This post will dive deep into why this happens, address the historical context, and provide practical, modern solutions for building robust