When you embed a hyper-link in any email in Outlook on web in Office 365, it automatically embeds the preview of the that url. This preview can result into a badly organized email, when you want the text to make an impact.

1. When you compose an email, to explicitly remove the preview from the message, you have to click on “Remove preview” as shown in the image.
2. To permanently disable this automatic preview feature, select “Settings” from the navigation bar. From the drop-down, select “Options” as shown in the image.
3. In the “Options” window, select “Link preview” under “Layout” from the left navigation (refer the image).
4. In “Link preview” window, uncheck  “Preview links in email” and click “Save“.
5. In case, you want to enable this feature, follow the steps 2, 3 and 4 and check the checkbox.