Why are the images in the email broken?
There is a separate FAQ related to images in the email not being the ones you expect, but if the images are actually broken, then something else may be going on.
What you can start by doing is right clicking on the image and grabbing the image URL:
Then, open that image up in a separate window. In this case, we're seeing a 404 error:
So, instead of actually returning the image, it's returning a 404 error page which is causing a broken image. This tends to be caused by missing path in the URL. For example, example.com/en/ instead of example.com, which can be changed in the Settings > Store Domain.