By default, an email folder is not shared. You (the Grantor) can share your email folder with anyone (the Grantee).
Note: An Inbox is an email folder. As an example, you might share an Inbox to a departmental (non-person) email account (e.g. firstname.lastname@example.org) with everyone in the office so that they can view and reply to email messages as they are received. Once they have Manager access to the Inbox, they can reply to messages "on behalf" of the email address (email@example.com) directly from their own email account. Once they are done, they can then file the message in another shared folder (e.g. Completed) for future reference.
Another example might be that someone (a Proxy) manages your email messages. You can share your Inbox and any folders with the Proxy sot that they can respond to messages on your behalf, organize your mail, and delete messages.
Follow these directions to share an email folder: