Gmail for organizations

Good day.
You need to drag the entire office to the gmail, and this question arose:
There is an existing and long-running office site, for example, test.com . Need mailboxes like username@test.com. But what will happen to the site, because we are changing the MX and the like ... And I think that the site will stop working. I can’t find a specific answer in the Google Help, but I can only write to the support service already registered there.
Maybe someone came across and tell? Is it possible to do what you want?
Thanks in advance.