Link previews allow people receiving your email to see a small snippet of the URL you're sending. This is very useful if you're sending property URLs as it gives an insight into what the property is before clicking on the link.
How to Use Link Previews
When composing emails, the links that are pasted in will automatically be converted to a nice preview.
If you do not want a link preview to appear, then you can click Show as URL to show the link without a preview or Remove to completely remove the URL.
Most problems with link previews involve an invalid URL. In order to validate your URL, you can simply open a new tab in your browser and paste the URL in. If it goes to the correct location, make sure to copy it directly from the browser.
Once you have the fresh copied URL you know is valid, paste the link back into the email. If no preview appears, it's because the website you're linking from doesn't have any relevant metadata to create a preview. You can choose to send the link as-is or hyperlink some text in your email instead.