HTML email preflight guide
How to test HTML email links and local assets
A campaign can look correct on the developer's Mac while referencing a file that never enters the upload bundle. Resolve every reference from the actual delivery folder.
Resolve local paths
Inventory relative image, font and attachment references against the selected package root. Flag a path that does not exist instead of letting WebKit silently show a broken element.
Classify remote resources
Keep remote images and links distinct from local assets. This makes the optional network check deliberate and keeps the base scan private.
Check response status
When you choose to contact remote URLs, record redirects, unreachable destinations and response codes so the finding can be reproduced.
Retain dynamic placeholders
Unsubscribe and tracking destinations may be provider placeholders rather than normal URLs. Validate their syntax without requesting them as if they were public web pages.