If clients want to have emails sent to one email forwarded automatically to another email you can use google workspace to set up email forwarding.

Note: if they want to forward the emails to an email account out of the organization they will have to use this instead:  

https://support.google.com/a/answer/4524505#auto-forwarding

https://support.google.com/a/answer/4524505#address-map-forwarding

This is also a good place to check if clients are wanting this disabled