Have no idea what is going on. I haven't been able to send or receive any email from my Mac using iCloud running Yosemite since yesterday. Nothing that I update on my Mac - Calendar, iCloud Drive, etc. gets updated on iCloud. I went into preferences and I am signed on. If I sign off, it says I will loose everything on my Mac. iCloud itself seems to be working fine between my iPad and iPhone, so it seems to be a Yosemite/Mac problem. Any suggestions?