Hi,

I have a fedora28 system with dovecot-2.3.5 and I'm trying to figure out why I'm increasingly receiving duplicate emails. The message IDs are exactly the same. It's always two of the same messages. I don't think it's ever occurred in the inbox. It doesn't happen with every message or seemingly in every folder.

I've read about dovecot deduplicate, but of course I want to prevent them from being duplicated in the first place. It's also happening much more frequently now.

Could something in my configuration cause this problem?

Below is the contents of my doveconf

# 2.3.5 (513208660): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.5 (2483b085) # OS: Linux 4.20.11-100.fc28.x86_64 x86_64 Fedora release 28 (Twenty Eight) # Hostname: orion.inside.guardiandigital.com # NOTE: Send doveconf -n output instead when asking for help. auth_anonymous_username = anonymous auth_cache_negative_ttl = 1 hours auth_cache_size = 0 auth_cache_ttl = 1 hours auth_cache_verify_password_with_worker = no auth_debug = no auth_debug_passwords = no auth_default_realm = auth_failure_delay = 2 secs auth_gssapi_hostname = auth_krb5_keytab = auth_master_user_separator = auth_mechanisms = plain auth_policy_check_after_auth = yes auth_policy_check_before_auth = yes auth_policy_hash_mech = sha256 auth_policy_hash_nonce = auth_policy_hash_truncate = 12 auth_policy_log_only = no auth_policy_reject_on_fail = no auth_policy_report_after_auth = yes auth_policy_request_attributes = login=%{requested_username} pwhash=%{hashed_password} remote=%{rip} device_id=%{client_id} protocol=%s auth_policy_server_api_header = auth_policy_server_timeout_msecs = 2000 auth_policy_server_url = auth_proxy_self = auth_realms = auth_socket_path = auth-userdb auth_ssl_require_client_cert = no auth_ssl_username_from_cert = no auth_stats = no auth_use_winbind = no auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@ auth_username_format = %Lu auth_username_translation = auth_verbose = no auth_verbose_passwords = no auth_winbind_helper_path = /usr/bin/ntlm_auth auth_worker_max_count = 30 base_dir = /var/run/dovecot config_cache_size = 1 M debug_log_path = default_client_limit = 1000 default_idle_kill = 1 mins default_internal_group = dovecot default_internal_user = dovecot default_login_user = dovenull default_process_limit = 100 default_vsz_limit = 256 M deliver_log_format = msgid=%m: %$ dict_db_config = director_flush_socket = director_mail_servers = director_max_parallel_kicks = 100 director_max_parallel_moves = 100 director_output_buffer_size = 10 M director_ping_idle_timeout = 30 secs director_ping_max_timeout = 1 mins director_servers = director_user_expire = 15 mins director_user_kick_delay = 2 secs director_username_hash = %u disable_plaintext_auth = yes dotlock_use_excl = yes doveadm_allowed_commands = doveadm_api_key = doveadm_http_rawlog_dir = doveadm_password = doveadm_port = 0 doveadm_socket_path = doveadm-server doveadm_username = doveadm doveadm_worker_count = 0 dsync_alt_char = _ dsync_commit_msgs_interval = 100 dsync_features = dsync_hashed_headers = Date Message-ID dsync_remote_cmd = ssh -l%{login} %{host} doveadm dsync-server -u%u -U first_valid_gid = 1 first_valid_uid = 500 haproxy_timeout = 3 secs haproxy_trusted_networks = hostname = imap_capability = imap_client_workarounds = imap_fetch_failure = disconnect-immediately imap_hibernate_timeout = 0 imap_id_log = imap_id_retain = no imap_id_send = name * imap_idle_notify_interval = 2 mins imap_literal_minus = no imap_logout_format = in=%i out=%o deleted=%{deleted} expunged=%{expunged} trashed=%{trashed} hdr_count=%{fetch_hdr_count} hdr_bytes=%{fetch_hdr_bytes} body_count=%{fetch_body_count} body_bytes=%{fetch_body_bytes} imap_max_line_length = 64 k imap_metadata = no imap_urlauth_host = imap_urlauth_logout_format = in=%i out=%o imap_urlauth_port = 143 imapc_cmd_timeout = 5 mins imapc_connection_retry_count = 1 imapc_connection_retry_interval = 1 secs imapc_features = imapc_host = imapc_list_prefix = imapc_master_user = imapc_max_idle_time = 29 mins imapc_max_line_length = 0 imapc_password = imapc_port = 143 imapc_rawlog_dir = imapc_sasl_mechanisms = imapc_ssl = no imapc_ssl_verify = yes imapc_user = import_environment = TZ CORE_OUTOFMEM CORE_ERROR LISTEN_PID LISTEN_FDS info_log_path = instance_name = dovecot last_valid_gid = 0 last_valid_uid = 0 lda_mailbox_autocreate = no lda_mailbox_autosubscribe = no lda_original_recipient_header = libexec_dir = /usr/libexec/dovecot listen = *, :: lmtp_hdr_delivery_address = final lmtp_proxy = no lmtp_proxy_rawlog_dir = lmtp_rawlog_dir = lmtp_rcpt_check_quota = no lmtp_save_to_detail_mailbox = no lmtp_user_concurrency_limit = 0 lock_method = fcntl log_core_filter = log_debug = log_path = syslog log_timestamp = "%b %d %H:%M:%S " login_access_sockets = login_greeting = Dovecot ready. login_log_format = %$: %s login_log_format_elements = user=<%u> method=%m rip=%r lip=%l mpid=%e %c session=<%{session}> login_plugin_dir = /usr/lib64/dovecot/login login_plugins = login_proxy_max_disconnect_delay = 0 login_proxy_notify_path = proxy-notify login_source_ips = login_trusted_networks = mail_access_groups = mail_always_cache_fields = mail_attachment_detection_options = mail_attachment_dir = mail_attachment_fs = sis posix mail_attachment_hash = %{sha1} mail_attachment_min_size = 128 k mail_attribute_dict = mail_cache_compress_continued_percentage = 200 mail_cache_compress_delete_percentage = 20 mail_cache_compress_header_continue_count = 4 mail_cache_compress_min_size = 32 k mail_cache_fields = flags mail_cache_min_mail_count = 0 mail_cache_record_max_size = 64 k mail_cache_unaccessed_field_drop = 30 days mail_chroot = mail_debug = no mail_fsync = optimized mail_full_filesystem_access = no mail_gid = mail mail_home = mail/ mail_index_log2_max_age = 2 days mail_index_log_rotate_max_size = 1 M mail_index_log_rotate_min_age = 5 mins mail_index_log_rotate_min_size = 32 k mail_index_rewrite_max_log_bytes = 128 k mail_index_rewrite_min_log_bytes = 8 k mail_location = mbox:~/mail:INBOX=/var/spool/mail/%u mail_log_prefix = "%s(%u)<%{pid}><%{session}>: " mail_max_keyword_length = 50 mail_max_lock_timeout = 0 mail_max_userip_connections = 500 mail_never_cache_fields = imap.envelope mail_nfs_index = no mail_nfs_storage = no mail_plugin_dir = /usr/lib64/dovecot mail_plugins = " listescape" mail_prefetch_count = 0 mail_privileged_group = mail mail_save_crlf = no mail_server_admin = mail_server_comment = mail_shared_explicit_inbox = no mail_sort_max_read_count = 0 mail_temp_dir = /tmp mail_temp_scan_interval = 1 weeks mail_uid = mail_vsize_bg_after_count = 0 mailbox_idle_check_interval = 30 secs mailbox_list_index = yes mailbox_list_index_include_inbox = no mailbox_list_index_very_dirty_syncs = no maildir_broken_filename_sizes = no maildir_copy_with_hardlinks = yes maildir_empty_new = no maildir_stat_dirs = no maildir_very_dirty_syncs = no managesieve_client_workarounds = managesieve_implementation_string = Dovecot Pigeonhole managesieve_logout_format = bytes=%i/%o managesieve_max_compile_errors = 5 managesieve_max_line_length = 65536 managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext master_user_separator = mbox_dirty_syncs = yes mbox_dotlock_change_timeout = 2 mins mbox_lazy_writes = yes mbox_lock_timeout = 5 mins mbox_md5 = apop3d mbox_min_index_size = 0 mbox_read_locks = fcntl mbox_very_dirty_syncs = no mbox_write_locks = fcntl mdbox_preallocate_space = no mdbox_rotate_interval = 0 mdbox_rotate_size = 10 M mmap_disable = no namespace inbox { disabled = no hidden = no ignore_on_failure = no inbox = yes list = yes location = mailbox Drafts { auto = no autoexpunge = 0 autoexpunge_max_mails = 0 comment = driver = special_use = \Drafts } mailbox Junk { auto = no autoexpunge = 0 autoexpunge_max_mails = 0 comment = driver = special_use = \Junk } mailbox Sent { auto = no autoexpunge = 0 autoexpunge_max_mails = 0 comment = driver = special_use = \Sent } mailbox "Sent Messages" { auto = no autoexpunge = 0 autoexpunge_max_mails = 0 comment = driver = special_use = \Sent } mailbox Trash { auto = no autoexpunge = 0 autoexpunge_max_mails = 0 comment = driver = special_use = \Trash } order = 0 prefix = separator = subscriptions = yes type = private } old_stats_carbon_interval = 30 secs old_stats_carbon_name = old_stats_carbon_server = old_stats_command_min_time = 1 mins old_stats_domain_min_time = 12 hours old_stats_ip_min_time = 12 hours old_stats_memory_limit = 16 M old_stats_session_min_time = 15 mins old_stats_user_min_time = 1 hours passdb { args = auth_verbose = default default_fields = deny = no driver = pam master = no mechanisms = name = override_fields = pass = no result_failure = continue result_internalfail = continue result_success = return-ok skip = never username_filter = } passdb { args = auth_verbose = default default_fields = deny = no driver = pam master = no mechanisms = name = override_fields = pass = no result_failure = continue result_internalfail = continue result_success = return-ok skip = never username_filter = } pop3_client_workarounds = pop3_delete_type = default pop3_deleted_flag = pop3_enable_last = no pop3_fast_size_lookups = no pop3_lock_session = no pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, size=%s pop3_no_flag_updates = no pop3_reuse_xuidl = no pop3_save_uidl = no pop3_uidl_duplicates = allow pop3_uidl_format = %08Xu%08Xv pop3c_features = pop3c_host = pop3c_master_user = pop3c_password = pop3c_port = 110 pop3c_quick_received_date = no pop3c_rawlog_dir = pop3c_ssl = no pop3c_ssl_verify = yes pop3c_user = %u postmaster_address = postmaster@%{if;%d;ne;;%d;%{hostname}} protocols = imap pop3 quota_full_tempfail = no rawlog_dir = recipient_delimiter = + rejection_reason = Your message to <%t> was automatically rejected:%n%r rejection_subject = Rejected: %s replication_dsync_parameters = -d -N -l 30 -U replication_full_sync_interval = 1 days replication_max_conns = 10 replicator_host = replicator replicator_port = 0 sendmail_path = /usr/sbin/sendmail service aggregator { chroot = . client_limit = 0 drop_priv_before_exec = no executable = aggregator extra_groups = fifo_listener replication-notify-fifo { group = mode = 0600 user = } group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 0 type = unix_listener replication-notify { group = mode = 0600 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service anvil { chroot = empty client_limit = 0 drop_priv_before_exec = no executable = anvil extra_groups = group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 1 protocol = service_count = 0 type = anvil unix_listener anvil-auth-penalty { group = mode = 0600 user = } unix_listener anvil { group = mode = 0600 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service auth-worker { chroot = client_limit = 1 drop_priv_before_exec = no executable = auth -w extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 1 type = unix_listener auth-worker { group = mode = 0600 user = $default_internal_user } user = vsz_limit = 18446744073709551615 B } service auth { chroot = client_limit = 0 drop_priv_before_exec = no executable = auth extra_groups = group = idle_kill = 0 privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } unix_listener auth-client { group = mode = 0600 user = $default_internal_user } unix_listener auth-login { group = mode = 0600 user = $default_internal_user } unix_listener auth-master { group = mode = 0600 user = } unix_listener auth-userdb { group = mode = 0666 user = $default_internal_user } unix_listener login/login { group = mode = 0666 user = } unix_listener token-login/tokenlogin { group = mode = 0666 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service config { chroot = client_limit = 0 drop_priv_before_exec = no executable = config extra_groups = group = idle_kill = 4294967295 secs privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 0 type = config unix_listener config { group = mode = 0600 user = } user = vsz_limit = 18446744073709551615 B } service dict-async { chroot = client_limit = 0 drop_priv_before_exec = no executable = dict extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 0 type = unix_listener dict-async { group = $default_internal_group mode = 0660 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service dict { chroot = client_limit = 1 drop_priv_before_exec = no executable = dict extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 0 type = unix_listener dict { group = $default_internal_group mode = 0660 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service director { chroot = . client_limit = 0 drop_priv_before_exec = no executable = director extra_groups = fifo_listener login/proxy-notify { group = mode = 00 user = } group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener director-admin { group = mode = 0600 user = } unix_listener login/director { group = mode = 00 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service dns_client { chroot = client_limit = 1 drop_priv_before_exec = no executable = dns-client extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 0 type = unix_listener dns-client { group = mode = 0666 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service doveadm { chroot = client_limit = 1 drop_priv_before_exec = no executable = doveadm-server extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = service_count = 1 type = unix_listener doveadm-server { group = mode = 0600 user = } user = vsz_limit = 18446744073709551615 B } service imap-hibernate { chroot = client_limit = 0 drop_priv_before_exec = no executable = imap-hibernate extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = imap service_count = 0 type = unix_listener imap-hibernate { group = $default_internal_group mode = 0660 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service imap-login { chroot = login client_limit = 0 drop_priv_before_exec = no executable = imap-login extra_groups = group = idle_kill = 0 inet_listener imap { address = haproxy = no port = 0 reuse_port = no ssl = no } inet_listener imaps { address = haproxy = no port = 993 reuse_port = no ssl = yes } privileged_group = process_limit = 0 process_min_avail = 20 protocol = imap service_count = 0 type = login user = $default_login_user vsz_limit = 18446744073709551615 B } service imap-urlauth-login { chroot = token-login client_limit = 0 drop_priv_before_exec = no executable = imap-urlauth-login extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = imap service_count = 1 type = login unix_listener imap-urlauth { group = mode = 0666 user = } user = $default_login_user vsz_limit = 18446744073709551615 B } service imap-urlauth-worker { chroot = client_limit = 1 drop_priv_before_exec = no executable = imap-urlauth-worker extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 1024 process_min_avail = 0 protocol = imap service_count = 1 type = unix_listener imap-urlauth-worker { group = mode = 0600 user = $default_internal_user } user = vsz_limit = 18446744073709551615 B } service imap-urlauth { chroot = client_limit = 1 drop_priv_before_exec = no executable = imap-urlauth extra_groups = group = idle_kill = 0 privileged_group = process_limit = 1024 process_min_avail = 0 protocol = imap service_count = 1 type = unix_listener token-login/imap-urlauth { group = mode = 0666 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service imap { chroot = client_limit = 1 drop_priv_before_exec = no executable = imap extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 1024 process_min_avail = 0 protocol = imap service_count = 1 type = unix_listener imap-master { group = mode = 0600 user = } unix_listener login/imap { group = mode = 0666 user = } user = vsz_limit = 18446744073709551615 B } service indexer-worker { chroot = client_limit = 1 drop_priv_before_exec = no executable = indexer-worker extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 10 process_min_avail = 0 protocol = service_count = 0 type = unix_listener indexer-worker { group = mode = 0600 user = $default_internal_user } user = vsz_limit = 18446744073709551615 B } service indexer { chroot = client_limit = 0 drop_priv_before_exec = no executable = indexer extra_groups = group = idle_kill = 0 privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener indexer { group = mode = 0666 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service ipc { chroot = empty client_limit = 0 drop_priv_before_exec = no executable = ipc extra_groups = group = idle_kill = 0 privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener ipc { group = mode = 0600 user = $default_internal_user } unix_listener login/ipc-proxy { group = mode = 0600 user = $default_login_user } user = $default_internal_user vsz_limit = 18446744073709551615 B } service lmtp { chroot = client_limit = 1 drop_priv_before_exec = no executable = lmtp extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = lmtp service_count = 0 type = unix_listener lmtp { group = mode = 0666 user = } user = vsz_limit = 18446744073709551615 B } service log { chroot = client_limit = 0 drop_priv_before_exec = no executable = log extra_groups = group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = log unix_listener log-errors { group = mode = 0600 user = } user = vsz_limit = 18446744073709551615 B } service managesieve-login { chroot = login client_limit = 0 drop_priv_before_exec = no executable = managesieve-login extra_groups = group = idle_kill = 0 inet_listener sieve { address = haproxy = no port = 4190 reuse_port = no ssl = no } privileged_group = process_limit = 0 process_min_avail = 0 protocol = sieve service_count = 1 type = login user = $default_login_user vsz_limit = 18446744073709551615 B } service managesieve { chroot = client_limit = 1 drop_priv_before_exec = no executable = managesieve extra_groups = group = idle_kill = 0 privileged_group = process_limit = 0 process_min_avail = 0 protocol = sieve service_count = 1 type = unix_listener login/sieve { group = mode = 0666 user = } user = vsz_limit = 18446744073709551615 B } service old-stats { chroot = empty client_limit = 0 drop_priv_before_exec = no executable = old-stats extra_groups = fifo_listener old-stats-mail { group = mode = 0600 user = } fifo_listener old-stats-user { group = mode = 0600 user = } group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener old-stats { group = mode = 0600 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service pop3-login { chroot = login client_limit = 0 drop_priv_before_exec = no executable = pop3-login extra_groups = group = idle_kill = 0 inet_listener pop3 { address = haproxy = no port = 0 reuse_port = no ssl = no } inet_listener pop3s { address = 192.168.1.100 haproxy = no port = 995 reuse_port = no ssl = yes } privileged_group = process_limit = 0 process_min_avail = 0 protocol = pop3 service_count = 1 type = login user = $default_login_user vsz_limit = 18446744073709551615 B } service pop3 { chroot = client_limit = 1 drop_priv_before_exec = no executable = pop3 extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 1024 process_min_avail = 0 protocol = pop3 service_count = 1 type = unix_listener login/pop3 { group = mode = 0666 user = } user = vsz_limit = 18446744073709551615 B } service replicator { chroot = client_limit = 0 drop_priv_before_exec = no executable = replicator extra_groups = group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener replicator-doveadm { group = mode = 00 user = $default_internal_user } unix_listener replicator { group = mode = 0600 user = $default_internal_user } user = vsz_limit = 18446744073709551615 B } service stats { chroot = empty client_limit = 0 drop_priv_before_exec = no executable = stats extra_groups = group = idle_kill = 4294967295 secs privileged_group = process_limit = 1 process_min_avail = 0 protocol = service_count = 0 type = unix_listener stats-reader { group = mode = 0600 user = } unix_listener stats-writer { group = $default_internal_group mode = 0660 user = } user = $default_internal_user vsz_limit = 18446744073709551615 B } service submission-login { chroot = login client_limit = 0 drop_priv_before_exec = no executable = submission-login extra_groups = group = idle_kill = 0 inet_listener submission { address = haproxy = no port = 587 reuse_port = no ssl = no } privileged_group = process_limit = 0 process_min_avail = 0 protocol = submission service_count = 1 type = login user = $default_login_user vsz_limit = 18446744073709551615 B } service submission { chroot = client_limit = 1 drop_priv_before_exec = no executable = submission extra_groups = $default_internal_group group = idle_kill = 0 privileged_group = process_limit = 1024 process_min_avail = 0 protocol = submission service_count = 1 type = unix_listener login/submission { group = mode = 0666 user = } user = vsz_limit = 18446744073709551615 B } shutdown_clients = yes ssl = yes ssl_alt_cert = ssl_alt_key = ssl_ca = ssl_cert =