Transition from one server to another.

Terry Barnum terry at
Mon Jul 14 22:27:18 UTC 2014

On Jul 14, 2014, at 1:22 PM, Anders Wegge Keller <wegge at> wrote:

> A frind of mine and I are running a dedicated server, that among
> other things host mail for ourselves and friends and families. All in
> all about 15 different domains with 35-40 users. The machine in
> question is old, so we are doing a slow transition from the old server
> to the new one. So far, we've managed to move web hosts
> seamlessly. Due to the technical capabilities at some of the user
> base, it would be nice to get to a setup, where we can move individual
> users imaps from the old server to the new one, as we get the time to
> visit them.
> I have an idea how such a transition could go:
> 1. Upgrade the old dovecot 1.2.15 to 2.1.whateveritis from debian
>    squeeze backports.
> 2. Set dsync up to replicate mails from the old server to the new
>    server. I know that 2.2 is recommended, but with a limited amount
>    of user, I'm willing to take a performance hit.
> 3. Migrate my parents &c to use the new server.
> 4. When all users have been moved on to using the new server, upgrade
>    MX records for the domain to point at the new server.
> 5. When all MX records are updated, decalre success.
> Is this feasible, and what would the risks be. For instance, during
> step 4, mails are bound to arrive at bothe the old and new server for
> some time. Will this cause problems?
> Is there a simpler solution to the problem?
> -- 
> /Wegge
> Leder efter redundant peering af dk.*,linux.debian.*

I did this several years ago using imapsync to sync the accounts from an old server to a new server. Once all the accounts have been sync'd and you're ready to cut over to the new server, run imapsync one last time to catch anything new that's arrived. It will go very quickly. Disable postfix/dovecot on the old server and change your DNS to point to the new server. Or better yet, if the old and new servers are on the same network, just swap the names and IPs of the new and old servers.


Terry Barnum
digital OutPost

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