Yes. Once a guest has bought a ticket to your paid event or registered to your free event, you will have access to their email address so that you can contact them regarding your event and ones to come.
You can see this on your app Guest Ticket List or GTL. To get there go to side menu and select My Hosted Events > Guest Ticket List.
The image below shows the app GTL. You can also download the detailed GTL. Just tap the export icon shown by the arrow in the image below. This will send you an excel spreadsheet with all the detail about your guest registrations.
If you have any questions, you can contact us at firstname.lastname@example.org.