On 31 Dec 2018, at 12.22, Ignacio García <yo@ignasi.com> wrote:
A totally different approach (that is imap-server agnostic), providing that you're setting up those new accounts with temporary passwords (which you know), before users change their passwords to their liking: you could also use imapsync ( https://github.com/imapsync/imapsync) . We here use it with a batch file and a text file containing all accounts to do mass-migrations, usually at night, when there's little to none user interaction with their mail accounts. I like this approach because mail service never gets interrupted and we do programmed syncs all night in case DNS propagation takes more than expected and mail still arrives to the old server.
I still don't recommend to use imapsync for migrations as UIDVALIDITY and UID numbers will change and end users will need to invalidate their local client caches and redownload all mail headers and usually also mail bodies again.
Sami