What does the gear icon on the prospect list allow you to do?

A company wants to send emails from a new domain.
Where should an Admin navigate to in Pardot to add the new domain?

What would make the Salesforce connector become unverified?

You want to export a list of prospects, but you only need the default fields. What can you use?

The marketing team thoroughly test emails before sending them. This includes being able to view the links and variable tags as prospects will see them.
Which Pardot feature of email flow could be used to run these tests?