Disappearing emails from my Inbox

I have problems with my email. Yesterday I lost all my Inbox messages from both my iPad and iPhone, but NOT my Macbook Pro. In my Settings (iCloud - Mail) I had it Active for the iPad and iPhone but not for the MacBook. I am more than concerned that the same thing may happen again. Can someone advise. I should also add, that occasionally in the past month, I have suddenly had my complete Inbox repeated i.e. I receive all the emails that i have held in the Inbox, sent to me again. Ideas?!