Finally I found a workaround to not depend on sendmail to forward messages using sieve:
In postfix main.cf I have: authorized_submit_users = root, filter (I want only root and filter to use sendmail and block other users to send e-mails from system accounts. Only allow users to send e-mails from virtual accounts and after smtp authentication. Username filter is used for bogofilter and needs access to sendmail) And in dovecot.conf: submission_host = 138.201.248.xxx The same workaround maybe works for NoNewPrivileges too as the authorized_submit_users setting in postfix has similar result.
