Sorry for the late update.
The first step was finished and emails can now be carbon copied to contact’s alternative emails. To do so the contact fields which store the alternative emails must be explicitly marked on the email setting page.
Unsubscribing will unsubscribe all alternative emails simultaneously because they all belong to the very same account. The person clicking “unsubscribe” is warned about this on the unsubscribe page.
For now we paused the development of this feature. but not for good. :) So I’m changing this wish status back to “collecting comments”.
Thank you everyone for a valuable feedback.Nancy commented
When we will be able to add a secondary email account. We have a number of members who need email copies sent to their secretary or the accounting dept to pay renewals.