courier to dovecot migration

[tovises]

>
> On 29.9.2019 23.38, tovises via dovecot wrote:
>> I have a quite old home server based on Debian 6.x packages using
>> courier
>> imap server (exim4, fetchmail, courier, apache2, squirrelmail) to keep
>> my
>> and my wife emails (about 25G).
>> I want renew my server to Debian 10 (buster) and got a recommendation to
>> use dovecot instead of courier. For this purpose I'm using a different
>> PC
>> as a sandbox. Debian 10 currently offer dovecot version 2.3.4.1
>> Installation was "peaceful" but stuck with the migration. I have choose
>> migration using dsync, from Wiki I was choose this command:
>>
>> For per-user user/passwords use:
>>
>> doveadm -o imapc_user=foo -o pop3c_user=foo -o imapc_password=bar -o
>> pop3c_password=bar backup -R -u user at domain imapc:
>>
>> (foo and bar placed real username and password)
>>
>> But I get error:
>> doveadm(tovis at nusi.tovis-lab.mydomain.org): Error: User doesn't exist
>>
>> Strongly I have no real domain, I'm using "freedns". "nusi" is the local
>> name of my old server, "tovis-lab" is conjunction with "mydomain.org"
>> choose from freedns. I was trying short as "nusi" which is in /etc/hosts
>> file even ip address but the same result. 143 and 943 ports are working
>> only inside the firewall (OpenWrt).
>> I was checked using telnet courier on the "remote" box and dovecot on
>> the
>> localhost. I was able to login.
>>
>> What should I use as "user at domain" in this situation?
>>
>>   tovis
>>
>>
>>
> Hi!
>
> -u parameter should be your *local* username, @domain is optional.
>
> Aki
>
>
>
Thank you Aki for quick response!
Where i should define the remote IMAP server address/hostname?
My localhost run dovecot, remote host (other box) running courier.
The user name is the same (password too).
-u tovis
gives me "Error: Failed to initialize user: Namespace ''; Mailbox list
driver imapc: missing imapc_host"

Sincerely
  tovis