MySQL supports another type of pattern matching operation based on the regular expressions, REGEXP operator used for pattern matching.
SELECT * FROM `users`, WHERE `email` REGEXP '^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,63}$';
And now for your question of tracking multiple tables, you can use comma seperated table names right?
SELECT * FROM `users`, `customers`, `clients` WHERE `email` NOT REGEXP '^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,63}$';