The concept of a shared mailbox is straightforward—an entire Exchange Mailbox can be shared among multiple users who are all able to access and act on messages, calendar items, and contacts within the shared mailbox.
Typically these can utilize dedicated shared mailboxes which have e-mail addresses assigned to them, or access between user mailboxes can be granted and managed in the same way, such as access by a Personal Assistant or Secretary to a Manager's mailbox.
A dedicated shared mailbox is often associated with a role or a function within a business, such as a sales team, and it provides an ideal way to ensure that messages sent to a team are stored within a central mailbox, rather than stored in individual mailboxes.
The following diagram shows how the mail flow is received by the shared mailbox and can stay within the shared mailbox only, and is accessed as a secondary mailbox by mailbox users:
This isn't the only way available in Exchange Server 2010 to...