No. When you delete a user, you permanently delete the email account and all messages associated with it.
Before deleting, you can ask the user to forward any messages that you'd like to keep or back up email using a desktop email program.
When you delete an email user, you also delete all of the user's associated email addresses, including aliases. Before deleting a user, you can reassign these aliases to someone else in your organization. This allows you to preserve the addresses for future use, although you will still lose any messages already received by the current user.