Most of the mailing lists supported at UD act as "mail reflectors." That is, one email message sent to one address is "reflected" (forwarded) to multiple addresses.
Shared mailboxes do not generate multiple copies of an email message. Instead, one message gets sent to one inbox shared by several people. Shared mailbox setup differs depending on whether everybody who need access to the shared mailbox:
Shared mailboxes can be used when there is a need to create a special ID for an organization or department.