[Dovecot] Migrating from dovecot 2.1 to 2.2

[Micah Anderson]

Due to the incompatibilities with the dsync protocol version between 2.1
and 2.2, I am unable to use dsync to move users to a new machine where
we have 2.2.5 setup. This wouldn't normally be a problem, as I could
just rsync the user's mdbox and dovecot would happily do the right
thing. However, on the new system I've placed the indexes into a faster
storage medium, where on the older system the indexes were included in
their mail directory.

I can rsync over the entire thing, including their old indexes, and
dovecot will try to do the right thing and build new indexes, but what
happens is all mail is marked as unread, and I get some old index cruft
left around in the directories.

How can I preserve the seen/unseen flags in such a migration? 

Thanks!
micah