[Dovecot] Gotchas in switching from one server to another without impacting users?

[Gary Chodos]

We have to replace one mail store (foo.example.org) with another
(bar.example.org).  I rsync'd the maildirs from foo to bar today and
the plan is to hold all delivery (in the SMTP server) on foo over the
weekend, rsync again (this time it should be much faster since the
large xfer already occurred today), then flush the SMTP queue on foo
towards bar, direct all new deliveries to bar.example.org.  Users
currently access their IMAP mailboxes via imap.example.org.  I plan to
just 'flip the switch' at DNS so imap.example.org points to
bar.example.org (instead of foo.example.org) so users don't have to
change anything on their end and should not even notice this change.

Is there anything else I should think about to mitigate users noticing
a change?  Does the fact that the mail filenames include
'foo.example.org' in the file name (while new deliveries to
bar.example.org will include that new hostname) spell trouble later on
or can I ignore it?  Is there a more efficient way to achieve my goal?

And finally, dovecot on foo.example.org is 1.1.7 while the new server
is running 1.1.16.  I don't think that should be an issue, but
mentioning it just in case.

Thanks!

--
GC