My main and largest client has 3 IT Techs in house.  They want the ticket replies for their users to come from their corporate email addresses (Or at least appear to), but still have the system track all threads between technician and end user until resolution.  Is there a way to accomplish this without creating a Federation between our corporate O365 Tenant and the Client's?  I have been at infrastructure and application role outs for 21 years (Specializing in Citrix, you get pretty strong at rolling out many different applications!), but I cannot wrap my head around a configuration that will work without a federated connection of the two O365 Tenants when using Exchange Online.

Any suggestions are appreciated greatly!

-ddub