Transactional emails are usually triggered based on a customer's action with a company. To be qualified as transactional or relationship messages, these communications' primary purpose must be "to facilitate, complete, or confirm a commercial transaction that the recipient has previously agreed to enter into with the sender" along with a few other narrow definitions of transactional messaging. Triggered transactional messages include dropped basket messages, password reset emails, purchase or order confirmation emails, order status emails, reorder emails, and email receipts.
If links and looks are set, begin interacting with the page. Abandon it, adjust the window size, convert. Are error messages appearing when they’re supposed to (if, for example, you don’t input all the form’s required info)? Is your CTA button working? If you abandon the page, are you retargeted with ads? When you resize the window, does your landing page respond accordingly?