Syncing two mail servers?

[Knute Johnson]

I currently have a mail server using Dovecot and sendmail.  I was 
thinking I would like to have a backup of my mail and an additional 
server in case of hardware failure.  Is it possible to run two identical 
or nearly identical server setups and sync the mail files between them?  
If it is possible, in general terms how would one go about this?

Thanks,
--

Knute Johnson