In this post, Pioneer Web Design show how PVWD is Using phpMyAdmin To Get Registered Users Email Addresses.
I have been asked this before: “How can I get all my registered users email addresses?”
One way is to use phpMyAdmin, the MySQL database tool used by most (good) hosts. If you are not both an advanced user and know how to backup your database, do not even continue to read as an error there can destroy your database and therefore your site!
SELECT COUNT(*) AS `Rows`, `user_login`, `user_email` FROM `wp_users` GROUP BY `user_login` ORDER BY `user_login`
This will output a table with the user login and their email used when they registered for your site. Once the query is run, the table can be exported to a variety of formats.
Note: phpMyAdmin allows you to build your own queries and run them.