How to create MySQL trigger -

i have table users 2 fields id (numeric) , email (with full email adress) how add trigger can prevent adding new email records specific domains eg: *@somedomain.com?

the trigger this:

delimiter $$  create trigger user_insert before insert on user     each row begin   if new.email '%@somedomain.com'     signal sqlstate '99999'         set message_text = 'invalid domain';   end if; end$$   delimiter ;