me.com has stopped downloading mail to my ipad, I can see it in iCloud on my iMac

I'm sure this question has come up a 1000 times before, but I cant find any answers.

My me.com account has stopped downloading emails, 'failed to connect to server'.

I can send emails but not receive. I haven't changed any or touched any settings.

Yet when I look in iCloud from the iMac I can see and read the emails there?