I followed all the requirements detailed in https://doc.dovecot.org/main/installation/upgrade/2.3-to-2.4.html, but there seems to be an issue on my side configuring correctly the Mailbox locations. In 10-mail.conf, I changed the mail driver from: mail_driver = mbox --> mail_driver = dbox I thought that would be sufficient but apparently, it is not the case.

All updated configurations are: dovecot -n

2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf

Pigeonhole version 2.4.1-4 (0a86619f)

OS: Linux 6.17.0-8-generic x86_64 Ubuntu 25.10

Hostname: <hostname>

dovecot_config_version = 2.4.1 auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain auth_verbose = yes auth_verbose_passwords = sha1 dovecot_storage_version = 2.4.1 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes log_debug = category=ssl log_timestamp = "%Y-%m-%d %H:%M:%S " mail_driver = dbox mail_home = /home/%{user|username} mail_inbox_path = /var/mail/%{user} mail_path = %{home}/mail mail_privileged_group = mail protocols = imap lmtp ssl = required ssl_cipher_list = <some list> ssl_curve_list = <some list> ssl_min_protocol = TLSv1.3 passdb pam { driver = pam fields { allow_nets = <nets> } result_failure = return-fail result_internalfail = return-fail result_success = return-ok skip = never } userdb passwd { } namespace inbox { inbox = yes mailbox Drafts { special_use = "\\Drafts" } mailbox Junk { special_use = "\\Junk" } mailbox Trash { special_use = "\\Trash" } mailbox Sent { special_use = "\\Sent" } mailbox virtual/All { special_use = "\\All" } } service imap-login { inet_listener imap { port = 143 listen = 127.0.0.1 [::1] } inet_listener imaps { port = 993 ssl = yes listen = * [::] } } service pop3-login { inet_listener pop3 { } inet_listener pop3s { } } service submission-login { inet_listener submission { } } service lmtp { inet_listener lmtp { port = 8024 listen = 127.0.0.1 ::1 } } service imap { } service pop3 { } service submission { } service auth { unix_listener auth-userdb { } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { } service dict { unix_listener dict { } } ssl_server { ca_file = <path> cert_file = <path> key_file = <path> prefer_ciphers = server request_client_cert = yes require_crl = no } ssl_client { ca_dir = /etc/ssl/certs require_valid_cert = yes } protocol lmtp { auth_username_format = %{user | username} mail_plugins = quota sieve postmaster_address = <email> }

In mail.err, I get multiple error messages such as: Error: Mailbox INBOX: open() failed with file /var/mail/<user>/dovecot.index.log: Not a directory of course, because /var/mail/<user> is not a folder but a file containing all the received mails.

So, in /var/mail, I have one file per user, plus one user.lock.sav, and also some weird files such as mu8xTBeL, muaBkJQL... belonging to one of the user.

How should I configure dbox?