Unfortunately, there’s no foolproof method to disable Gmail’s auto-scaling via email code. Through extensive experience, I’ve found that Gmail’s mobile app tends to overlook many viewport controls you implement. Instead of battling with this, I adopt a design strategy that accounts for scaling. I ensure my base template is already optimized for mobile displays, foregoing reliance on media queries. Utilize larger font sizes in your inline CSS—aim for at least 16px for body text—and ensure images have high contrast to maintain clarity when scaled down. The viewport meta tag commonly used on web pages is ineffective in email contexts, as Gmail often removes these tags. It’s best to conduct thorough testing with auto-resize enabled and modify your design as needed, since most users do not change the default setting.