[Dovecot] migrate 15K users to new domain name

[Jan-Frode Myklebust]

I need to migrate 15K users to a new domain name, and plan to use "dsync
mirror" in the transition phase. Could someone confirm that this should
work:

Before giving users access to new-domain do a first sync to get all the
stale data over:

        for user in $old-domain; do
                dsync mirror $user@old-domain $user@new-domain
        done

Configure sieve vacation filter to forward all messages from
$user@old-domain to $user@new-domain, and notify sender of changed
address.

Give users access to both new-domain and old-domain, and do a final
sync.

        for user in $old-domain; do
                dsync mirror $user@old-domain $user@new-domain
                dsync mirror $user@old-domain $user@new-domain  # twice in case 
the first was slow 
                drop all messages for $user@old-domain
                Leave notice message for $user@old-domain saying he should use 
new-domain
        done

Wait a few weeks/months, and then drop all users@old-domain.


Does this look sensible? 


  -jf