Doveadm on director

https://doc.dovecot.org/admin_manual/doveadm_mailbox_commands/

As indicated in the documentation above, in case of configuration with the director, the doveadm commands must be executed from the director itself. However, if I try to run the command "doveadm -D mailbox list -u user@example.com" the command fails because it tries to lookup user locally instead on one of the backend servers.

Where am I wrong?

My configuration consists of three directors and three backend servers.

Thanks a lot.