The public Mail page now says that a team admin can make a mailbox private to one member, and that only that member can open it. It also describes Add common addresses and when an address can be set to refuse mail instead of going to the catch-all. Help articles for Bookmarks and Time Tracking now end with a link to support.
Mail page describes private team mailboxes
The Mail feature page now explains private team mailboxes, common role addresses and how refused addresses work with a catch-all.