Best way to move mail from one server to another

[Sami Ketola]

> On 4 Sep 2018, at 10.20, James Brown <jlbrown at bordo.com.au> wrote:
> 
> I’d like to migrate to a new server. I only need to transfer the mail store, have already done the users. I’ve seen different recommendations:
> 
> IMAP-Sync
> Rsync
> Doveadmin backup and
> dsync
> 
> What are the pros and cons of each? What would be best for me? I’m thinking that Doveadmin backup is the way to go.
> 
> Both old and new servers are on same network. New server is running Dovecot 2.3.2.1, old server is 2.2.32. macOS X.
> 
> Does anyone have any advice or examples?


It depends. Are your users already receiving mails to the new server? If yes, then the only way is to use "doveadm sync -1" or data will be lost. Even then data may be lost as UID numbers might already be used in the new server.
If your users are not receiving mails to the new server it still depends. Is the mail storage format same in both servers? If yes, then it's probably fastest to use rsync. If not, then you need to use doveadm backup.

imapsync always loses data.

Sami