email redirection question

[Dan Coutu]

I'm using a sendmail server as the primary mail server and have setup a 
new server running Open Xchange to eventually replace it. I'd like to 
move people to the new server one by one in order minimize confusion and 
chaos. Currently the firewall sends all incoming email to the old mail 
server. I'd like to move people to the new system one by one and then 
change the firewall forwarding rule once everyone has been migrated. I'm 
wondering what techniques folks would recommend for managing this 
transition?

A few different possibilities come to mind: use a .forward file in each 
user's home directory, setup a sendmail filter rule for each person, or 
share the /var/spool/mail directory between the two systems.

Thanks!

Dan