CC Emails into CRM when email is hosted on another server

Client wants to be able to CC emails so they are imported into the correct client/project in the CRM. They are going to continue hosting their domains email on a third party server (Google in this case). I would assume we will need to setup a second domain hosted on the same server as the CRM in order to do this. Correct?

the cc’ed email just needs to be a imap account, doesn’t need to be on the same server as the crm, then you can add it to the inbound email for it to be imported