I don't have any advise to moving to gmail for a corp email.
I do recommend moving to your own email servers. That way you could have something like
bob@yourcompany.com. That looks like a company I want to deal with and receive email from.
If you send me a quote request or bill payment request from
bob@gmail.com it'll go straight to the trash as spam.
Setting up a email server for your company should cost zero dollars and about 15 minutes. It may take 4 or 5 hours of research if you are doing it.
I'm sorry I couldn't directly help you with gmail as I've never created a gmail account for clients, I have moved many away from gmail though. PM me if you decide to move away from gmail and I'll save you 4 hours research.