Exchange 2000 Failover Planning

I am planning the Exchange 2000 rollout for a relatively small company. Currently we use external internet mail. I need to be able to have some kind of high availability with Exchange 2000 but the company does not want to spend the money on clustering service.

Are there any other ways I can safely accomplish this by having a mailbox with an outside company that replicates my server so that should it go down and I need a day to rebuild, we will not loose mail??