Re: Issue upgrading from 2.3.x to 2.4.1 when changing the mail driver from mbox to dbox

18 Jan 2026


      ...
On 01/16/2026 10:50 AM MST actionmystique via dovecot <dovecot@dovecot.org> wrote:
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.
Changing mailbox format requires migration. See https://doc.dovecot.org/latest/core/admin/migration.html
michael
...
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?

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Re: Issue upgrading from 2.3.x to 2.4.1 when changing the mail driver from mbox to dbox

Michael Slusarz

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>