Disable Link Preview feature in Outlook
In Outlook on the web, when you write an email and add a URL, or when you receive an email with URL inside it, you get a rich preview that includes a link title, thumbnail, and description of the link. This is called Link preview.
Instead of this: http://www.microsoft.com
With Link preview, you get this:
To turn this feature off Refer Microsoft Office article at http://support.office.com/en-ie/article/Add-a-link-to-an-email-using-Link-Preview-ebbfd8ce-d38e-40ef-bb8c-a5362e881163
Additional Information: http://www.msoutlook.info/question/disable-enable-link-preview-outlook-365-web