On 28/05/2026 02:15 EEST Jean-Daniel Beaubien via dovecot <dovecot@dovecot.org> wrote:

Hi,

I currently have a doveadm backup running my prod and backup server. Both are currently running 2.3.16, and the following command runs fine:

sudo doveadm -v backup -u XXXX -P remote:XXXX@192.168.111.XX

I am in the process of updating my servers to ubuntu 26.04 which runs dovecot 2.4.2 and I am running into problems trying to run this command.

For some reason, it tries to delete the INBOX on the destination and I get the following error: dsync-remote(XXXX)<7hkbKDl6F2rlxQAArPp36Q>: Error: brain S: Mailbox INBOX sync: mailbox_delete failed: The /private/specialuse attribute cannot be changed doveadm(228686): Error: Remote command returned error 65: ssh -lXXXX 192.168.111.XX doveadm dsync-server -uXXXX

I am not sure what/why this is happening. I read the docs and man page, but could not find a solution.

Anyone knows what is happening, and how to solve this?

Thanks,

-JD

----- Addendum -----

Another thing that might help someone else: I had to add a line to the config file to avoid the -U problem:

dsync_remote_cmd = "ssh -l%{login} %{host} doveadm dsync-server -u%{user}"

This seems to already be solved ( https://dovecot.org/mailman3/archives/list/dovecot@dovecot.org/thread/B3TQFA...), but not yet in the ubuntu 26.04 release? Hi, I currently have a doveadm backup running my prod and backup server. Both are currently running 2.3.16, and the following command runs fine: sudo doveadm -v backup -u XXXX -P remote:XXXX@192.168.111.XX I am in the process of updating my servers to ubuntu 26.04 which runs dovecot 2.4.2 and I am running into problems trying to run this command. For some reason, it tries to delete the INBOX on the destination and I get the following error: dsync-remote(XXXX)<7hkbKDl6F2rlxQAArPp36Q>: Error: brain S: Mailbox INBOX sync: mailbox_delete failed: The /private/specialuse attribute cannot be changed doveadm(228686): Error: Remote command returned error 65: ssh -lXXXX 192.168.111.XX doveadm dsync-server -uXXXX

I am not sure what/why this is happening. I read the docs and man page, but could not find a solution. Anyone knows what is happening, and how to solve this? Thanks, -JD ----- Addendum ----- Another thing that might help someone else: I had to add a line to the config file to avoid the -U problem:

dsync_remote_cmd = "ssh -l%{login} %{host} doveadm dsync-server -u%{user}"

This seems to already be solved ([1]https://dovecot.org/mailman3/archives/list/dovecot@dovecot.org/thread/B3TQFA...), but not yet in the ubuntu 26.04 release?

Hi!

I would recommend looking at our migration guide, https://doc.dovecot.org/latest/core/admin/migration.html

This sounds like your config might be interfering here.

Aki