There are several common sizes that marketers test:
1. Full Width (600px): Ideal for desktop but can be resized for mobile. 2. Responsive Design: Adjusts to the screen size of the device automatically. 3. Short vs. Long Emails: Short emails often lead to higher engagement, but long emails can provide more detailed information. 4. Image-Heavy vs. Text-Heavy: Testing the balance between images and text is crucial for engagement.