I think this page[1] is not correct If you configure this option: imapsieve_mailbox1_before = file:/usr/lib/dovecot/sieve/report-spam.sieve the file report-spam.svbin cannot be created because users cannot write there. [1] https://doc.dovecot.org/configuration_manual/howto/antispam_with_sieve/#howto-antispam-with-imapsieve