1. Mail filters distrust .html files
Attackers have long sent fake login forms as HTML attachments, because an attached page can run JavaScript and imitate any website once opened. As a result many company mail gateways quarantine or strip .html and .htm attachments, and some providers show a warning banner on them. Your perfectly innocent newsletter preview can vanish before the recipient ever sees it.
2. Phones are bad at opening them
Tap an HTML attachment on Android and you are often asked which app to use — and the list may include text editors that show raw code. On iPhone, Quick Look shows a simplified preview where scripts may not run and interactive parts stay dead. Neither experience is what you designed.
3. The other files are missing
Most pages reference other files: style.css, app.js, images/hero.jpg. Attach only the HTML and the recipient's copy looks for those files next to itself, finds nothing, and shows unstyled text with broken images. Attaching a ZIP fixes that, but now the recipient has to unzip, find the right file and open it — few will.
What to send instead: a link
- Links are what every inbox and chat app is designed for — they show a preview card and open in one tap.
- The page renders in the recipient's real browser, scripts and all.
- CSS and images load because they sit on the same server.
- You can fix a typo after sending, and the same link shows the corrected page.
Convert the HTML file to a link, paste the link into your message, and keep the file to yourself.
When a file is still the right choice
Send the file when the recipient needs to edit the HTML (a developer taking over), when the content must never touch a third-party server, or when it is an archive copy for records. In every other case — “please look at this” — send a link.