I want to see my customers list only with their email addresses. Can I do this with one of reports in QBO?

Hi there, 

Welcome back to the Community. It's important you're able to view a report which shows you your customer's emails.

To view this, you'll have to run a Customer Contact List Report. You can find this report by clicking Reports from the left navigation menu and searching for report using the search field.  Once you have the report pulled up, you can customize it so you can see the customer emails. Here's an image for visual reference:

Give this a try and let me know how you make out. I'm here if you need further assistance.