It would be nice to see a history of any changes to an email address for individual contacts. When I look at a contact's history of messages sent, sometimes there are bounces, or an account gets suspended. We do try to reach out the people to update the addresses and often do update the address. Of course I would expect that later messages sent would then get through, but this isn't always the case. When I'm looking at a contact and see that messages are bouncing or not, it would be nice to know when an email address had been updated.