Message Size

Through the Internet Mail Service, we set the default size for incoming and outgoing messages to 5MB. Now if we set individual mailbox incoming and outgoing messages sizes to a different value (1MB) through the Limits tab in Microsoft Exchange Administrator, which one would take precedence?

In addition, is there a way to block all attachments to a particular user and to retrieve those blocked attachments from the Exchange Server? (or are they just returned to the user)

Thanks,
Dan