Is it safe to mix dovecot import/backup/sync between dovecot versions 2.2.30.2 and 2.3.7.1?

[Sami Ketola]

> On 22 Dec 2019, at 12.22, Gerben Wierda <gerben.wierda at rna.nl> wrote:
> 
> I am migrating a server. The old one uses dovecot 2.2.30.2 and the new one 2.3.7.1. I don’t want to use any tool that might influence flags on messages. I am using Maildir format on both ends and I have a way to let one server access the data on the other (either using an rsync or a direct access).
> 
> Could I set up a sync between both to create a smooth migration?

rsync probably works out fine, but I would use native dovecot dsync myself. 

Something like this run on the new server:

/usr/bin/doveadm backup -u <userid> -R ssh adminuser at old-server "sudo /usr/bin/doveadm dsync-server -u <olduserid>"

Sami