Emails on my icloud account

All of my emails disappeared as of a couple of hours ago. Emails in Trash, Archive,Sent and Junk are still there. I have an iPad and iMac. The emails have disappeared on these devices too?

Is there an explanation as to why the emails disappeared?

I have an iCloud back up also extra storage (50G) that I pay for each month.

This is the second tome in a matter of approx 4 months that this has happened to me.