The store driver saves the message to the hard disk drive using Ntfsdrv.dll. The messages are saved to the queue directory in the \Exchsrvr\Vs1\Mailroot directory. If the message is addressed to a local domain, the message is then moved to the specified drop directory, which is \Exchsrvr\Vs1\Mailroot Drop by default.

When Exchange 2000 is installed, it adds another store driver (Drviis.dll) to communicate with Web Storage System by using ExIPC. After adding a new local domain, the system is capable of delivering messages to either Web Storage System (using Drviis.dll) or the file system (using Ntfsdrv.dll).