Follow the instructions on the screen, and when you’re satisfied you can go ahead and publish it for the world to see. By default, sites created with Website will follow the domain structure: “yourcompanyname.business.site.” A custom domain can be purchased from the Settings menu in your account, and Google will automatically connect your site with the new domain.
One of the most important compatibility factors to consider with email is the mobility question. How often do your employees need to access email via mobile devices? That's an important issue because most email hosting providers deliver some kind of web client usable as a default inbox. Almost all of these can be accessed via a mobile device, so if your employees don't need to access their emails on the road that much, then such mediocre clients are probably fine.