Abstract: The present invention is a system that uses a migration server to access voicemail of a source system through a front-end switch via a telephony interface, obtain voice messages stored on the source system and store them on a destination system via a data interface. A host processor initiates a migration based on a mailbox migration status stored in a host database and controls the switch to provide a path from the migration server to the source system. The host processor also controls call flow and initiates pass code (PIN) digit capture of a subscriber's pass code by the switch for mailboxes to be migrated. Call flow control includes determining to which system to route an arriving call based on migration status and determining whether to output a message-waiting indicator for newly stored messages. A migration server controls call tree navigation aspects of call flow during migration.