Mail migration from old hosting provider to dovecot

Question

Unable to find a decent tutorial on this and the dovecot wiki doesn't seem to specify much other than the command line parameters for doveadm sync.

I need to move emails from a hosting provider to a new server I've set-up (time-bound on this before the old hosting provider charges for another year). The new server has been set-up with postfix and dovecot. These have been configured in the following manner.

Dovecot does authentication
Dovecot file holds users and passwords
2 x domains set-up (example.com and example2.com)

This set-up works for inbound and outbound for example.com and example2.com.

Old hosting provider with domain oldexample.com holds several mailboxes to be migrated. While I can access the server via SSH it is extremely locked down so no root access or even access to install anything. If I've understood correctly I can use dovecot on the new email server to pull the accounts using the dsync utility via IMAP.

The questions I have (before I start) are

1. Do I need to create the users from oldexample.com on the new server before I attempt the sync?
2. Do I need to add the domain oldexample.com to the new server config before or after I attempt the sync?
3. When should the MX records etc for oldexample.com be updated - presumably after the sync?

Any help appreciated or if there is a tutorial out there with this information (and any other relvant info) that I've missed please point me in that direction.

Answer 1

After a bit of playing around I managed to figure it out - details below for anyone who comes across this (presuming your postfix and dovecot is set-up as detailed above - which was setup as per https://www.binarytides.com/install-postfix-dovecot-debian/).

1. Add the domain to be migrated to /etc/postfix/virtual_mailbox_domains
2. Add the users to be migrated to the user auth file (/etc/dovecot/dovecot-users)
3. Add migration config to /etc/dovecot/conf.d/migrate.conf (taken from https://wiki2.dovecot.org/Migration/Dsync)
4. For each user run the below command (updating the username)

    doveadm -D -v -o mail_fsync=never backup -R -u user@oldexample.com imapc:

5. Update DNS/MX records