SBS 2008 includes a brand new version of the POP3 connector. This post will introduce key elements in understanding how this version differs from previous versions and how to implement it properly. Like its predecessors, the POP3 connector in SBS 2008 is meant to be a migration solution to allow companies to transition from hosting their email at the ISP to hosting their email in-house on Exchange server. It is highly recommended to retire the POP3 Connector once your migration is complete and allow Exchange 2007 to directly host email for your domain.
Full Article: SBS Blog