what could have been the causes of closure of some yahoo mail account recently?

Answer 1

Well, if you've tried signing in as many times as you've asked this question then you might've lock it up! LOL! okay j/k They may have just temporarily closed it to transfer it to their new system. Unless, of course, you've abused the privelage somehow, which I doubt. Just wait it out and keep trying for a couple days, then ask again ;-)