Update Contact Mail for a Lead

When someone sends a reply from a mail adress different to the lead mail, i want to

a) See this in the UniBox (right now i only see this when i click on the reply button and check for the adress my reply is sending to)

and b) be able to change / update the contact mail of the Lead without losing the connection of the lead to the Conversation.

(Right now, when i change the mail adress, i cannot then edit the status of the lead, since the connection of the conversation to the lead is severed, since the conversation still has the old adress marked).