Preview and test your campaign
You can preview what your design looks like in a specific subscriber's mailbox and even send a test to your own mailbox to see what an email to that subscriber would look like.
Preview
Click on the Preview & test button in the top-right corner above the editor. Then, select one of the contacts on your list from the drop-down menu to view the email exactly as that subscriber would see it in their mailbox.
The default preview shows no personalisation, but you can choose any contact from the drop-down menu or search for a specific contact on your list by typing its email address in the search box.
Test
You can send your email as a test to view how it will be displayed in an actual mailbox. To do it, click on the Send as a test button in the top-right corner and select the email address(es) you want to send it to. If you selected a specific contact in the Preview field, the email will appear as if it was being sent to that subscriber, so all personalisation will be populated.
And here's what you'll see in your mailbox:
The Preview and test option is available in campaigns and automated emails. It won't work in a template, as they aren't linked to a specific list. You can learn more about it here.