P> On 15/05/2020 10.56, Gregory Sloop wrote:
>> IMAP sync looks better and better. I'm a little puzzled why I don't just give up walking on the broken glass and use it - but it just bugs the heck out of me.

P> If you can get the dovecot native sync to work, it seems to be a
P> better option, as it understands all the dovecot index formats etc,
P> and will transfer those correctly. Imapsync doesn't, and when I did
P> that I had a few problems with POP email clients re-downloading
P> their entire Inbox, which produced a few groans. Your mileage may vary.

P> Another option for you, if you have the time and energy would be
P> to set up proper replication between the two servers. Then any
P> changes made would be synced in real time, until the cutoff, when
P> you just shut down the old server and the new one is already up to
P> date. But if you can't get a simple sync happening then that might be a bit of over-reach.

P> My suspicions on your current situation would center around the
P> complications introduced by docker, and on file/container
P> permissions, environment variables, paths etc.

P> How about if you just try a simple doveadm command over ssh from
P> the remote server to make sure that works. eg. from "Sending" server do

P> ssh root@po.abc.net \
P>  docker exec b3093cxxxxxx doveadm user user@abc.net

P> That should execute the doveadm user command on the remote
P> (receiving) server. If that works, then at least you can satisfy
P> yourself that the docker bit is working correctly. Not sure why I'm
P> getting involved in someone else's troubleshooting nightmare! ;-)

doveadm user does work.
i.e.
ssh root@abc.net docker exec b3093c6200a9 doveadm user user@abc.net

I get the uid/gid/home/maildir of that account, etc.

I do appreciate the help you've given!