Best way to move mail from one server to another

[Sami Ketola]

> On 4 Sep 2018, at 18.38, Robert Schetterer <rs at sys4.de> wrote:
> 
> Sorry i migrated terrabytes of mail with imapsync and never had a
> problem, it works as designed, also with maildir rsync did a good job,
> what never worked as it should was dsync ,cause of bugs ,that may
> changed now
> 

I would like to very much hear about the problems you had with dsync as we have successfully migrated tens of petabytes of mails with it successfully while preserving the UID numbers.
Imapsync would have been totally out of question as it is absolutely crucial in those migrations to keep the UID -> MAIL pairs matching legacy server. And usually also POP3 UIDLs. If not keeping the data the servers would have literally melted under load when switching over then of thousands of users forcing them to redownload headers of even mail bodies for millions of mails.

Sami