Another book from Hentzenwerke Publishing available from Amazon: “Send and Receive Your Domain Email with Gmail.”
Whil tackles a number of different ways in which you can use Google’s Email facilities to send and receive email just as if you were running a big company and were paying for someone to host your own domains email server, without the overhead, administration or security hassles.
Whil sets up a couple of different situations: one person with a bunch of domains, several people on one domain, several people several domains, and goes through ways these can be configured via your ISP and Google to allow you access to email all in one Inbox or separately. There are also some very useful asides.
Check it out at: https://www.amazon.com/Send-Receive-Domain-Email-Gmail/dp/1930919107