A- The main difference lies in the fact that a shared mailbox is associated with a disabled user account, whereas a user mailbox is associated with an active user account. Shared mailboxes are intended to be used by multiple users who need access to the same information, but for security or permission reasons, do not require their own user accounts. A shared mailbox functions in the same way as a user mailbox, but it is designed with the explicit purpose of allowing multiple people to login & access its contents.