A question I’m frequently asked by users is “What happens to a user’s mailbox in the event they leave the company?”.
My first response is usually to qualify what’s going to happen with their email address once they’ve left. Will the address leave with them and will all further messages sent to that address will be bounced? Or will there be another member of staff taking over their role who’ll need visibility of those existing messages?
This is a decision for the business and companies will differ from each other in how they’ll want to approach the managing of mailboxes and of staff turnover.
Typically I find that companies will remove the Active Directory account as soon as the person has left, and they’ll probably also choose to remove the email account from the mail server. Most organisations will tend to keep the email archive for this user intact for some time.