This is a feature I wish my programs I’m using to read email had. Sometimes, some people change email address. It happens, to some more than to others. When that happens I don’t change the email address for that person in my contact list. I add the new address.
The reasons is that I still want to maintain an association between all those emails I’ve sent and I received from that person and the contact details for that person. The idea is that when I ask my software for all emails from “John Smith”, even if John Smith changed addresses 15 times, it should still be able to find the old ones.
The problem is that sooner or later I send an email to that person using the obsolete email address. I really wish the software would allow me to mark addresses as obsolete or historic so that the information is not lost but I never use them again.