What I did when I changed mail servers was this:
1. deny incoming connections to old-server from my LAN (to stop my users
from sending mails)
2. allow qmail to process the queue (is there a way to force qmail to
process the queue instead of waiting for it to finish?)
3. tar the users' Maildirs
4. move the tarball to new-server and untar
5. unplug cable to old-server and plug it into new-server
That's it. Note that old-server and new-server have the same IP so I didn't
have to do any DNS changes (make sure you unplug the old one first before
plugging in the new one or there'd be an IP conflict). So far we haven't
noticed any problems but I may have just been lucky. Do the filenames in
the Maildirs also correspond to inode numbers? If so then I guess I really
am just lucky :) My "technique" gave us a downtime of 1 hour but this was
mostly taken up by waiting for the queue to be processed by qmail, otherwise
it would just have been at most 10 minutes.
M. Yu
