[Exim] OK I admit it this is a stupid question

Folks,

    I need a bit of reassurance here.  I currently have a server for a domain
on one network and need to move it to a different network.   My thought was
to set up the second server on the new network configured to accept  the
domain mail, re-configure the original server to act as a secondary MX
server copy the mailboxes to the new server and then fire up the new
server's exim process to start accepting the inbound email.

    What I need to understand is this...

In DNS I will set newhost as MX value = 5 and the oldhost MX value = 10

remove the domain from local_domain and put it in relay_domain on the old
host.

and finally just restart the exim process kill -HUP process_id


am I missing anything here. It just seems way too simple..

Thanks for the help

Kevin B