Don't lose any of the dovecot-* files and your clients should be fine. I've done 1) a couple of times and nobody got hurt.What you should do is keep the two servers (the old and the new one), and once the new one is ready test with your client only (change your client's IMAP/POP server settings). Once you make sure it works right, you can change the config for the other clients. I have no idea about 2)

  -- Yassine.

On Monday, March 20, 2017 8:49 AM, Gandalf Corvotempesta <gandalf.corvotempesta@gmail.com> wrote:

Hi to all. It's time to migrate an old server to a newer platform

Some questions:

1. what happens by changing the pop3/IMAP server on the client? Is the client (Outlook, Thunderbird,...) smart enough to not download every message again? I'm asking this because the easier way to migrate would be move all mailboxes to the new server and then change the hostname on the client

2. what if I add a dovecot proxy on the new server, proxing back all requests to the older one, if the mailbox is still not migrated? Would the whole pop3/IMAP transaction happen through the proxy or there is something an http redirect (or anything similiar to the SIP protocol) ?

3. I think the response to this is no: is dovecot able to log the hostname used for the connection? I have multiple domains pointing to the same IP. Something like the Host header in Http.