Synchronizing Email Systems between servers

[Matthew Carpenter]

Hello all.  

Email Clustering question here.  I am using two linux boxes to cluster for
email services.  There will be a primary and a backup (hotswap, whatever you
want to call it).
These will be running Sendmail and the standard Inetd version of Pop3/s that
comes with RH8.
Does anyone have a good solution for keeping the two systems' email in sync? 
Or should we simple plan a backup using cronned scp or rsynch?

Thank you for your input.

Matt