WordPress Users & WooCommerce Customers Import Export plugin facilitates the import and export of users effortlessly. Alternatively, Quick Export allows exporting specific columns individually also. User Email is one among the column which appears for quick export. Therefore, just select the user_email column from the Quick Export section and unselect all other columns.
The steps involved in exporting user emails only are demonstrated below:
To get a detailed overview of how the users are exported, go to Setting up WordPress Users and WooCommerce Customers Import-Export Plugin