In Mail Connectors -> Connector Schedule, simply don't have any (enabled) schedules. Then VPOP3 won't automatically connect, and you'll have to connect manually.
To 'Connect Now', either to go Status -> Server Status and press 'Connect Now', or right-click the Status Monitor (the VPOP3 icon in the Windows task-tray) and select 'Connect Now' (just like in v1.4, if I can remember that far back ;-) )