Mailbox Replication

Hi can someone tell me if there is a way to replicate a single mailbox across 2 exchange servers. Ideally it would be real time replication just like cached mode…

at the moment i have the second server setup with outlook and i have opened the mailbox on the server using cache mode giving me a real time replication. However if the main server was to go down i would need to export the cache into a pst and then import into the second mail server.

Two questions.

1. Is there a way i can replicate the 2 mailboxes?

2. Is there a way i can import directly from a ost file into outlook?

Thank you.

Chris