In an email
Your images should be a minimum of 640px wide and a maximum of 1200px wide. If your images are wider than 1200px, they will automatically scale down to fit correctly as Alura's email templates are responsive.
If the image width is narrower than 640px wide, they won’t automatically stretch to fit and may look blurry. You can also choose to align the picture left, right, or centered. There are no height restrictions but bear in mind how the image will best appear to your users in an email.