How to use logo for emails
When adding an image under "Appearance > Logo and images" to be used for email messages, you should be aware of the following:
The image is used as a "header image", so it takes up the entire available width.
Example of an email message:

It is therefore very important that your image is wide and low.
It is often a better solution not to add an image under "Appearance > Logo and images". Instead, you can insert your logo directly on your order confirmation or in newsletters.