A company is going through a rebrand and want to change all of their google based company emails. EG: sales@stackoverflow.co.nz -> sales@stack.co.nz Is there any way this can be changed so they can carry on business as normal without having to tell everyone to use new addresses etc (email must appear to be sent from new domain also).
Thanks for your help not my area of knowledge.
Since maintaining the original domain's email doesn't cause any harm, just start forwarding the email from the old email addresses to the new ones at the new domain name. Then start sending and replying with your new domain name. If you're not going to tell people, then you might want to keep the forwarding going, renewing the domain name and so on.
Note: Of course, implement full email authentication - SPF, DKIM, and DMARC for both domain names.