Images not loading within the screenshots
There are several reasons why the images within your email screenshot previews may not be loading.
Linking to locally hosted images
Litmus does not provide image hosting, and your images will need to be either hosted on your server or through your Email Service Provider. You may want to check your email's HTML to make sure that you are not using local image links. If your image links are pointing to locally hosted images, then you will want to update these links to your hosted image URLs and then submit a retest.
Images stored within a testing environment or behind a firewall
If your images are hosted within a testing environment or behind a firewall, you can allow requests based on our user agent. We do not use static IPs for our asset retrieval, so allowing a single IP address or range of addresses would likely be ineffective.
When we download images, we always pass a user agent along that contains "X-Litmus-Image-Check". Many firewalls have the ability to allow requests based on user-agent strings, so hopefully, you can do so with that phrase. It's the recommended option as this will be consistent and won't change, unlike IPs.
Partially loaded images within your results
If you see images that have partially loaded or have an email result with one or two unloaded images, you may want to run a recapture for this result. This can be done by clicking on the result and then using the keyboard shortcut 'R' to generate a new screenshot or by using the Recapture image button (only appears in Checklist). This will usually resolve any partially loaded images within your email.