Anonymize wordpress user email addresses for cloning purposes. Exclude specific domain names to keep admin/selected users intact. Prefix so that addresses are still unique.

anonymize_wp_useremails.sql

SET @domains='domain1.com|domain2.com';
UPDATE wp_users prod_users,
  ( select ID FROM wp_users WHERE user_email NOT REGEXP @domains) clone_users
SET prod_users.user_email = CONCAT('DC_', prod_users.ID, '@example.org') 
WHERE prod_users.user_email NOT REGEXP @domains;