> On 4 Dec 2017, at 19.59, Webert de Souza Lima <webert.b...@gmail.com> 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 >> >> > 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