You probably know what a contact group is—it's what you use to send the same email to multiple people at the same time.
You need to set up an @email address before you can use i Cloud Mail.
If you didn't set up an i Cloud Mail account at the same time as i Cloud, the Mail option in your i Cloud for Windows account might be grayed out.
Finally I discovered that the 10.12.5 update didn't install all the way.
I downloaded the update from Apple's website and ran the package installer. Download can be found here, https://support.apple.com/kb/DL1917?
There's no downloadable demonstration file for this article.