On Tue, Dec 5, 2017 at 4:16 AM, Sami Ketola <sami.ket...@dovecot.fi> wrote:

> On Mon, Dec 4, 2017 at 9:16 AM, Sami Ketola <sami.ket...@dovecot.fi>
>  wrote:
>> With every other tool you will face end users needing to  invalidate
>> their local caches and
>> redownloading all headers if not also all mail bodies.
>> Sami
>> > On 4 Dec 2017, at 19.59, Webert de Souza Lima <webert.b...@gmail.com>
> wrote:
> >
> > I don't think so. Been using imapsync for large scale migrations from
> > external servers to our dovecot setup. Users don't even see it when the
> key
> > is switched (DNS changes).
> > Go for it.
> You are wrong. There is no way to assign IMAP UID:s over IMAP protocol. It
> simply does not support it.
> With imapsync there is absolutely no way to preserve them and you will
> face problems with IMAP UID:s
> not matching the cached mail anymore.
> Trust us. We have run multiple migrations at scale of 10+ million users.
> Sami

Sorry, I might be wrong about cache invalidation, indeed. What I'm sure is
that users will hardly notice any server change.
We've never had user complaints about mailboxes resyncing or anything like
that after imapsync'ing to a new server, that's why I'd recommend using
imapsync with no worries.

It's easy enough to test this on a single user account first and see how is
imap client's behavior after the DNS change.


Webert Lima
DevOps Engineer at MAV Tecnologia
*Belo Horizonte - Brasil*

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