Hi,

Suddenly I have a strange problem with the latest Outlook 365 (version 2506, build 16.0.1.18925.20076 64-bit) clients. When a user flags a message, they cannot remove the flag because Outlook gives an error message "The action cannot be performed because the message has been modified". One solution is to make the message unread and then remove the flag.

However, since the moment a user flags a message for the first time, the maillog contains delete/expunge loop endlessly, for example:

Jul 18 09:50:25 server dovecot: imap(user): delete: box=INBOX.Euro Brand, uid=2108, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597602, vsize=7698181, from="Masked User" <masked.user@somedomain.com>, subject=testing Jul 18 09:50:25 server dovecot: imap(user): expunge: box=INBOX.Euro Brand, uid=2108, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597602, vsize=7698181, from="Masked User" <masked.user@somedomain.com>, subject=testing Jul 18 09:50:27 server dovecot: imap(user): delete: box=INBOX.Euro Brand, uid=2109, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597628, vsize=7698214, from="Masked User" <masked.user@somedomain.com>, subject=testing Jul 18 09:50:27 server dovecot: imap(user): expunge: box=INBOX.Euro Brand, uid=2109, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597628, vsize=7698214, from="Masked User" <masked.user@somedomain.com>, subject=testing Jul 18 09:50:28 server dovecot: imap(user): delete: box=INBOX.Euro Brand, uid=2110, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597654, vsize=7698247, from="Masked User" <masked.user@somedomain.com>, subject=testing Jul 18 09:50:28 server dovecot: imap(user): expunge: box=INBOX.Euro Brand, uid=2110, msgid=<GV1P195MB16414FAC3D4BAC6326F956048351A@GV1P195MB1641.EURP195.PROD.OUTLOOK.COM>, size=7597654, vsize=7698247, from="Masked User" <masked.user@somedomain.com>, subject=testing

...

So the message UID will change indefinitely forever.

Is there any way to fix this with dovecot configuration?

dovecot -n

2.3.21.1 (d492236fa0): /etc/dovecot/dovecot.conf

auth_cache_size = 1 k auth_failure_delay = 1 mins auth_mechanisms = plain login base_dir = /var/run/dovecot/ default_client_limit = 2000 default_process_limit = 500 disable_plaintext_auth = no dsync_features = no-header-hashes import_environment = TZ CORE_OUTOFMEM CORE_ERROR TZ=:/etc/localtime MALLOC_MMAP_THRESHOLD_=131072 listen = * login_greeting = login_log_format_elements = %u %r %m %c %k mail_location = maildir:~/Maildir mail_log_prefix = "%s(%u): " mail_plugins = " mail_log notify" mail_sort_max_read_count = 100 mailbox_list_index_very_dirty_syncs = yes maildir_very_dirty_syncs = yes passdb { args = dovecot driver = pam } plugin { autocreate2 = Sent Items autosubscribe2 = Sent Items mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename mail_log_fields = uid box msgid size from subject vsize } protocols = imap service auth { unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0666 user = postfix } } service imap-login { inet_listener imap { port = 0 } inet_listener imaps { port = 993 ssl = yes } process_min_avail = 1 } service imap { process_limit = 2048 vsz_limit = 1 G } ssl_ca = </etc/ssl/certs/mail.ca.crt ssl_cert = </etc/ssl/certs/mail.fullchain.cer ssl_cipher_list = kEECDH:+kEECDH+SHA:kEDH:+kEDH+SHA:+kEDH+CAMELLIA:kECDH:+kECDH+SHA:kRSA:+kRSA+SHA:+kRSA+CAMELLIA:!aNULL:!eNULL:!SSLv2:!RC4:!MD5:!DES:!EXP:!SEED:!IDEA:!3DES ssl_dh = # hidden, use -P to show it ssl_key = # hidden, use -P to show it ssl_min_protocol = TLSv1 ssl_prefer_server_ciphers = yes state_dir = /var/run/dovecot userdb { driver = passwd } protocol imap { imap_client_workarounds = tb-extra-mailbox-sep tb-lsub-flags delay-newmail imap_idle_notify_interval = 15 mins imap_logout_format = %{rip}, bytes=%i/%o, del=%{deleted} mail_max_userip_connections = 500 }

-- Mart