Recently I upgraded dovecot quite a few major versions. Since then some mailboxes are experiencing deleted mail reappearing. It seems to be happening roughly once a day, but not for every mail client or mailbox, I have at least two clients with this issue: Thunderbird and Outlook.

Storage is local under two partitions, one as alternative storage.

# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.7.2 () # OS: Linux 5.4.0-29-generic x86_64 Ubuntu 20.04 LTS ext4 auth_mechanisms = plain login digest-md5 base_dir = /var/run/dovecot/ default_client_limit = 4000 default_vsz_limit = 512 M dict { expire = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext quota = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext } disable_plaintext_auth = no lda_mailbox_autocreate = yes log_timestamp = "%Y-%m-%d %H:%M:%S " mail_location = mdbox:/home/vmail/%d/%n mail_max_userip_connections = 240 mail_plugins = quota mail_privileged_group = mail mdbox_rotate_size = 64 M namespace { inbox = yes location = prefix = separator = . } passdb { args = /etc/dovecot/dovecot-sql.conf driver = sql } plugin { quota = dict:user_quota::proxy:/var/run/dovecot/dict:quota quota_warning = storage=95%% quota-warning 95 %u quota_warning2 = storage=80%% quota-warning 80 %u sieve = file:~/sieve;active=~/.dovecot.sieve sieve_dir = ~/sieve sieve_global_dir = /etc/dovecot/sieve/ } protocols = imap pop3 service anvil { client_limit = 2615 } service auth { client_limit = 5536 unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } unix_listener auth-master { group = root mode = 0600 user = vmail } } service dict { unix_listener dict { mode = 0600 user = vmail } } service imap-login { client_limit = 2115 executable = /usr/lib/dovecot/imap-login inet_listener imap { address = * port = 143 } inet_listener imaps { address = * port = 993 } process_limit = 2000 } service imap { executable = /usr/lib/dovecot/imap process_limit = 2000 } service pop3-login { client_limit = 1024 executable = /usr/lib/dovecot/pop3-login inet_listener pop3 { address = * port = 110 } inet_listener pop3s { address = * port = 995 } process_limit = 512 } service pop3 { executable = /usr/lib/dovecot/pop3 } service stats { unix_listener stats-reader { group = vmail mode = 0660 user = vmail } unix_listener stats-writer { group = vmail mode = 0660 user = vmail } } ssl_cert = < /etc/dovecot/ssl/crt.pem ssl_cipher_list = ALL:!LOW:!SSLv2:!EXP:!aNULL ssl_client_ca_dir = /etc/ssl/certs ssl_dh = # hidden, use -P to show it ssl_key = # hidden, use -P to show it ssl_prefer_server_ciphers = yes syslog_facility = local0 userdb { args = /etc/dovecot/dovecot-sql.conf driver = sql } protocol imap { imap_max_line_length = 64 k mail_plugins = quota imap_quota } protocol pop3 { mail_plugins = quota pop3_uidl_format = %08Xu%08Xv } protocol lda { auth_socket_path = /var/run/dovecot/auth-master mail_plugins = quota sieve postmaster_address = postmaster@localhost sendmail_path = /usr/lib/sendmail }

dovecot-sql.conf:

driver = mysql connect = host=127.0.0.1 dbname=mail user=mail password=#### password_query = SELECT IF('%m' = 'DIGEST-MD5', users.password_digest_md5, NULL) as password, IF('%m' = 'DIGEST-MD5', NULL, 'Y') as nopassword, username FROM users LEFT JOIN domains ON users.domain = domains.domain WHERE users.username = '%u' AND users.domain = '%d' AND users.active = 'yes' AND domains.state = '1' AND ((users.password = encrypt('%w', LEFT(users.password, 11)) AND ('%m' = 'PLAIN' OR '%m' = 'LOGIN')) OR ('%m' = 'DIGEST-MD5')) user_query = SELECT maildir as home, uid, gid, CONCAT(CONCAT(type, ':', maildir), ':ALT=/home/altmail/%d/%n') AS mail FROM users LEFT JOIN domains ON users.domain = domains.domain WHERE users.username = '%u' AND domains.state = '1' iterate_query = SELECT SUBSTRING_INDEX(email, '@', 1) AS username, domain FROM users;