Please note: The information in this article might be deprecated. It will be updated soon.
You can upload images that are available in the entire license by going to Setup → Media assets. You can manage this media library according to your preferences by creating a folder structure that is clear and organized for you.
If you upload an image that is available license-wide, you can use this image from all of your emails. This means it’s an excellent solution for images you often use, like your logo.
You could use this method for all of your images, but we strongly discourage it. After a while, you will have so many images in your media library that you might lose track of them. You also can't restructure the folder system because then the links in the emails you already sent won’t be correct anymore.